I watched it last night, and I'm not a chopper / motorcycle guy at all, even though I followed the series for the last year or two. As a matter of fact, my ideal would be something like a 2WD chopper, which, doesn't really exist as far as I can tell. I didn't vote but, I wouldn't be surprised to learn that the majority of viewers / voters weren't bikers or motorcycle enthusiasts either.
Junior's bike deservers the win in my opinion mainly because it is was the best looking, custom built chopper.
Senior's bike clearly had the manufacturing prowess hands-down but, it lacked any overarching aesthetic (curved, sloping lines in the back, industrial-angled forks) and I think that is the biggest difference between Senior's designer, and Junior. Honestly, I don't know if I'd call it a chopper either, it looked really small compared to Senior.
Gasmonkey's bike while beautiful, and good performing, was simply not a custom build. I've seen snippets of their show and I never got the impression that they do anything other than restoration and modification.
Jesse's bike looked to me nothing at all like a chopper, and if the commentary about the oil pan location was true (claimed to be under the seat), that couldn't be good either. It struck me as a hack to make a chopper set of components fit a streetbike form factor, minus all the aerodynamic panels you'd see on a streetbike.
If you ask me, I would really like to know who placed third- I'd hate to think that Senior's shop and Jesse would be on the same level.