Dax F80 Little Evil vs. Piston Bikes RaceJet?

So I've got a question for y'all...I'm looking at building a bike and possibly adding a SBP shift kit to it down the road and wanted to hear y'alls opinions between these two motors.

Links for reference:

1. That's Dax F80: http://thatsdax.com/ (It's the second engine down in the middle)

2. Piston Bikes RaceJet: http://www.pistonbikes.com/Motorized-Bicycle-Race-Engine-p/1pbrj.htm

Thanks!

my kits come with top end apart, guess I could say engines built in USA, but I don't

no matter what you buy, it will only be as good as it was built onto a bike by you and taken care of during use by you

there are kits I like & kits I don't, but there isn't a truly significant difference between them

I bought that Dax F80 back in March, and it has been a daily driver ever since. Very smooth. I added an RT carb and it turns a 41 gear easily.