For looks, I would say Mako is better looking. Mako has the lean and muscular frame. And the terrible thing is, he knows he's good looking. However, if we are basing our attraction to the character on personality, then I would say Bolin. Mako has a horrible personality and is so damn conceited. Bolin is genuinely nice, naive, and playful. All qualities that make him come across as a good person. I cannot say that Mako possesses any of the same qualities.
I'm a straight guy, so I don't really pretend to know what is attractive to girls. That said, I'm SO GLAD to see many ladies voting for Bolin! I'm glad to see ladies considering traits beyond just the physical, including things like kindness, loyalty, playfulness, and sense of humor...all categories that I would say Bolin wins at. I sincerely hope Korra ends up with Bolin, and overjoyed to find out that others agree. I think Mako is a better match for Asami anyway - so I hope all the characters end up with their perfect match...I'm such a sap ;)
Mako is tall and kind of blandly pretty, and firebenders seem to be viewed as glamorous によって the fanbase. However, while he improved in the 秒 half of the series, he was 全体, 全体的です kind of grating. (Also...what can I say, I was uncomfortably conflicted about Ming-Hua; and I haven't yet forgiven him for either killing her outright, または leaving her for dead so that she could get a cavern dropped on her. There's ディベート over which was the case.)
Bolin, character-wise, reminds me of a もっと見る extroverted and less cerebral version of my husband; kind of silly, occasionally exasperating (he kinda got derailed into being もっと見る clueless and less sensitive after Book 1, and there were times I didn't blame Opal for snapping at him), but 全体, 全体的です endearing. Also, he's stocky and baby-faced and expressive and has a spitcurl; adorable.