I don't think neither of them is harder than other, but backgrounds take more time on planning and executing.When artist blocks happen, it could be good time to practice more on the fundamentals, like anatomy, perspective and gesture. 
I feel more comfortable drawing characters, because I have more practise drawing them. However, I am slowly gaining confidence in drawing environments, since I'm now drawing them all the time.
Drawing the environments your characters are in helps establish a sense of place. It helps the reader feel that the characters exist in a context, rather than floating in a vague void. The vague void works perfectly well for gag-strips and certain varieties of slice-of-life comics, but if you're doing something more along the lines of adventure or mystery or action, you're going to want people to feel like these places are well-defined and certain, or else they might get confused.
As for how to avoid artist block.... Just keep drawing, even if it sucks. Avoiding drawing something isn't going to a.) make it easier, b.) improve your skills at it, or c.) make it magically appear on the page. The only way out is through.
i love do backgrounds, just one thing: i have to remeber to myself to dont overd it (this mean it become impossible to understand where s it the subject in the background itself!!!)
btw, to avoid or kill the artist block, go to watch on a book (or live if u can) works done by ELITE artists from the past to the present. this ll give u a great push to go back to work.
I'm definitely more familiar about character sketches than backgrounds. I've been working on both recently, but I've been studying anatomy and composition more than perspective or detail. I've got a long ways to go.
I'd say backgrounds are harder. For me it's not just about drawing the backgrounds themselves, but also... actually finding a background/setting. For a lot of my strips (and ESPECIALLY the single-page ones) I just need the two or more characters talking and this could happen wherever, exactly where it is isn't important, so... I have a hard time actually finding a specific place to put them in? I guess they could be in some generic room setting if anything, but then I might also want to... keep that setting consistent if it's, say, "character"'s house, instead of just having a million different "rooms" each only used once just to have a setting/background?
At least I try making them more interesting - instead of just a blank white void I add in some color (typically variations of the character's "signature" color) and patterns. I consider that an improvement
Character sketches might sometimes be hard in the sense of "oh man, just how do I draw this pose looking right?, but at least tend to have a general idea about what I want it to look like, unlike backgrounds.
A lot of people think backgrounds are harder... but I just try to think of the backgrounds AS a character and give it as much personality as possible. I think about what sorts of things would be in that space and what happens in that space, the mood of the location. That helps me to design interesting backgrounds and keeps me invested in drawing them, since it can get kind of tedious drawing the same stuff over and over.
well at the beginning of my comic , the background were worse than the character now it has inverted. Which I find surprising since before I hated drawing backgrounds except trees, I love trees! But I notice still my backgrounds are still harder to do but are more rewarding I notice! It help a lot to have nice backgrounds that compliments your characters! Though art block is inevitable unless you see how much it add to your comic!
I am incapable of understanding 3D space and sense of depth, therefore backgrounds are pretty much the bane of my existence.
Backgrounds are pretty hard skill to tackle, especially when you make them really detailed. I got to say kudos to those who can make amazing backgrounds in a pinch. When I try to work on backgrounds I try to keep in mind of where I want the focus to go so that I won't have to worry about very thing thats happening in the background and more on what the character is saying. So I guess character sketches are a more easier route for me since I love drawing characters more than anything.
Backgrounds definitely take more effort for me. Fortunately since I started doing webcomics, it's been forcing me to do more backgrounds and gradually get used to them.
I am more comfortable in characters. But lately I have been using references for the backgrounds, which helps a lot.
I am bad at backgrounds.... i have a feeling i will never be as amazing at them as most people, at least not drawing them. I can do painting, and the funny thing is while backgrounds are easier to paint, characters are harder to paint for me, Its way easier to have the outline for me when making characters.
I've been told my backgrounds/environments are better than my characters, and I think it's probably true. It's a result of the fact that I like drawing environments more than people, perhaps because it seems more straightforward to me. Lately, however, I've been trying to put more effort into making my characters better, and as a result I haven't been doing as much with the environments. You see, what was happening was I would spend so much time on the environments that I'd run out of time to put as much detail into the characters. Both the characters and their environment are important, however, so it's important to put equal effort into them. Under the right circumstances, the environment can become a character in its own right.
Definitely look up references for backgrounds if you're stuck on a page. To answer your question, for me, characters are a bit difficult because I have to get the anatomy, proportions, posing and their expressions correct because part of telling the story is show how the characters act in the comic.
I find backgrounds way easier than characters. Especially natural ones, since a shrub for example is way less complicated in form than a human haha. I use lots of references from Studio Ghibli stills to learn how to paint environments. I find it helps a lot. I think a common problem some people run into when first painting environments is that they over-render the texture and details, when much simpler "blocky strokes" not only look more natural but also take less time.
For me designing characters is super easy and it's my favorite part. Backgrounds however - well I really had to force myself into making them. I used to just make a solid color and put a little texture to it but that wasn't cutting it and it looked out of place behind my characters. Best advice on it I ever got was to 'do it first' or next to first after you get your characters roughed out.
I found that google is my bestfriend when it come to backgrounds. You can pretty much image search for whatever you're looking for and use it as ref for your BG. I also use A LOT of building brushes in Photoshop. There are wuite a few sets out there that are really good and make your BG look like you spent hours on it (instead of just a few clicks). Once again googling 'building brushes + whatever program you use will get you what you need to make awesome BGs
ugh. ugghhhh i hate doing backrounds. i do them a lot but i haaate them. i usually have a rule in comics to have at least one backround a page to show where the characters are. and then if theyre just standin around and not going anywhere im allowed to just gradient the frak out of it for the rest of the page. but usually i fill in backrounds cuz i like the look of it. and i think ya just gotta like threaten yerself into finishing it cuz i dont know how else to get it done
characters are fun tho i like those. no complaints
Drawing Characters isn't as hard as making environments for me. I use perspective for bother, so as long as It follow those rules my drawing will look decent. Of course I love designing characters because I can apply many aspects of to their outfits like their personality and social class. As for the environment I draw them only when I need to , like the environments in the comic's world or the background for a picture. I will not go out of my way to draw environment on its own like hos I do with a character.