I would get the first one. The flat side carburettor is (argueably) a better design and it comes with hte K&N filter and an 18 tooth sprocket. The second kit has a good carb but it's just a larger version of what's already on there.
The wild card in this for me is the "the 34mm Turbulator". I don't know what that is or what it does or how it does it.
Any way, that's my opinion on the subject. I haven't done any modification work to a Bullet yet, but I do have extensive time warming up Vespa style 2 stroke engines. So thios is just klind of 'for what its worth'.