Re: for better or for worse???
Well, these china 2strokes are mostly the same - the different "brand" names primarily refer to the accessories that come with the kit and their respective quality.
Having said that - there are some minor(ish) differences in motors, some older versions have bushings instead of bearings (some people even prefer that), some come with a slant head, some have a larger wrist pin, some have slightly better castings... the list goes on, but there's not a lot of consistency.
While I like the 'Grubee Skyhawk' kits because of the better quality accessories, ThatsDax actually has slightly better motors (quality bearings/larger wristpins) or so I've heard - the important thing is to get yer kit from a reliable and trustworthy source, like ThatsDax, Spooky, or BikeBerry. I'm sure there's others - but I've not had dealings with them lol