Hyper 7 28 has a .28 6 port engine,
Hyper 7 TQ Sport .21 4 port engine,
Hyper 7 Black Edition .21 3 port engine.
Only had experience with the .21 3 port engine and it's easy to tune and pretty quick, clocked 40.0mph on my phones GPS with the standard 14tooth clutch bell.
The buggy is very tough, drove mine into a tree at full speed which stopped it dead (the sun was in my eyes) , expecting the worst it barely had a scratch on it somehow lol. I'd go for the Black edition out of the 3 or if you can stretch go for the Hyper 7.5 which I'm pretty sure comes with the same engine as the black edition.
The Hong Nor X1X CR is a buggy i'd definitely consider as an alternative to the Hyper 7 range as well mate.
Hope this helps.