I do both! There's a merit in learning how to freehand something and merit in using guidelines to make sure you get the best possible look from your work (and proportional, which is the bigger part with regards to guidelines). I also find that knowing how to do both is incredibly beneficial since it'll increase the speed with which you're able to accurtely protray a character/scene/etc. and your ability to recall correct proportions.
I find it's good to exercize trying both, as it only expands your skillset. There's no shame in guidelines or having to map out a scene; when making your art the best it can be any tool is a worthy one.The only time I don't use them is when I draw with ink, since, with ink, you can't erase so, having an idea as to what you want to make really helps. This is a picture I made without guidelines in ink a long time ago:

(It isn't perfect but, no piece ever really is, right? Hahah.) In contrast, I love making speed paints so I can share my process with my watchers/followers and I love the process of turning a hand full of sketchy lines into something that almost looks entirely different by the time you're done.
This is my most recent speedpaint and, yeah there are LOTS of times I go back and forth on what I want to make with it so, you can see my process of deciding as I go and guidelining the hell out of it, hahah.
So you see? Nothing wrong with using guidelines or not using them. Knowing how to do both just sets you up with a broad skillset to draw from. (Haha and either way, you have to practice like a fiend!) 