I like both!
I do tend to like pixel art more since it's usually smaller and signature friendly. I also like to admire the detail that goes into, lol.
I like the vector/drawn style as well, but only if it's done in a realistic style. I don't really like adopts that look too cartoonish or chibi-like. No offense to anyone! They're cute but not my cup of tea. Probably why I didn't stick around Neopets long. :P