In my very own personal opinion - brand name doesn't mean jack. They're all china built blocks, and there is little to no quality assurance.
The Grubee name has a couple things other's don't - in some of their newer models, they have steel lined cylinders, and they have certain innovations like the Super Rat (which is a very new model, beginning of this year I believe) and it's internal CDI and whatever modification there is to the internal porting on the cylinder. Though, they also brown nose the EPA, and that's why there's catalytic exhausts and the "new high performance carb" that we know and love as the CNSv2 (which is garbage). That protects their company, which is great for them, but the customers are the ones who suffer in that. *wow, ending rant now*
Myself, I ride Raw motors cause I just like to. They treat me well, have a pretty good warranty, and they've been around for a little while. Their kits come stock with NT carbs, 415 chain and non-cat exhausts, so there's not as much immediate replacing of stock stuff. Heck, their older nondished sprockets from a few years back actually were predrilled out for disc rotor mounts.
Most importantly though, I feel that you should just look at the accessories that come with the kits. Is it standard bike chain, or 410/415? Is the chain tensioner bearing'd? As well, always ask what's the warranty that the seller has?
I would really say get the cheaper of the 3, there's not much a difference and it has an NT carb.
What is modified on the Super Rat's jug/cylinder is the transfer ports from what I've heard.
