Hrm, looking at these I have no idea which one is more popular, so I'm just gonna swing for the fences with crit here.
My gut reaction was that I liked the top one better, because the lineart looks very clean and well done, especially compared the lack of definition on the character in the bottom one. The ruffles on the dress have a lot of nice detail and care put into them too.
On the other hand, the second image has better focus. The character is front and center, it's clear what's going on, and the colors work better together to set the scene.
The top image gives a nice full-body shot of the main two characters, but they're mostly just sitting there, wheras in the bottom image there's a clear action and stronger characterization; it's less like a formal introduction and more like you're sitting at the same bar with the character.
I guess if I knew these characters I might prefer buying a print of the first one, but sharing the second one on social media with fellow fans.