I really like both. Sketchy art has a lot of character though. You don't see much of it, when it's intended, at least.
What about you?
How about cool weighted lines or chunky cartoonly lines? Need more selection! D:
I like smooth, crisp lines. Thick or thin; depending on what the piece itself would be better suited to. I am ridiculously fussy when it comes to my line work, and I love seeing it. It just makes everything look clean to me.
I like messy lines sometimes, but I feel like it's hard to use that style without it looking like no effort has been put into it. x:

It depends on how it's used. Typically I'd prefer lineless over thin lines- way too many people misuse them and the image ends up looking static.
My favorite lines are weighted and sketchy, though!
Ohmy, I like the cool weighted one Kitty linked :o
Generally, I prefer clean lines over sketchy.
Is lineless an option? ^^' I like painted!
But if i would have to choose between those two I couldnt pick. I admire those who can pull off the solid lines cleanly and those who can make sketchy lines look more characterised then lazy wins it for me :3
I don't like lines that are all the same thickness. I think some people can pull it off, but tapering and adding weight to them can make the image move so much futher and together. <3
I really like clean lines with a little bit of weight, unless you're going for an edgy look or something. Then sketchy lines are great. ^^
Itty bitty tiny 1-2px lineart really ANNOYS me to work with. XD And when you resize it, you hardly see it at all!
Chunky lines, occassionally not even completed in some parts, is my choice. ;D
I like pencil lines, messy or clean. Sketchy lineart is brilliant when the artist can actually pull it off, and smooth is just as good.
The big chunky lines from Sonic Battle are AMAZING though. 8D
For me I like line weight and smooth lines (saddly how my art school has me trained). To me if it a -refined sketch (ie smooth lines, faint ones) but not one that you can't tell what it is, to me that's unprofessional. But if that's the point of the piece, its a different matter.
Smooth, clean lines all the way! Some people can pull off sketchy lines really, really well, but then again for others it just looks sloppy and rushed. XD
I do like a bit of tapering and weight thrown in there sometimes, though. It can be all the difference in the world!
I think sketchy lines have more of an edgy look, this looka bit more cooler in my opion.
I love to look at clean lines but drawing them makes me RAGE.
So I stick with cartoony.

I prefer clean lines but I also love sketchy art. It gives it a jagged feel and if you're doing "darker" stuff it can really enhance the piece. I personally tend to draw in jagged evil lines...not because I draw "dark" meaningful stuff xD but because I'll back through it afterwards with the eraser and smooth it all down to what I want :P Is a super long process but I suck at drawing pretty thing straight lines.