The reason OFNA seems like they make so many kits is a wierd one: they actually make no kits at all! They are a distributor who re-brands other companies products as their own. OFNA re-sells Hong Nor, and Ho Bao kits. When it comes to buggies, Ho Bao is really only responsible for one (even though it is probably the most popular buggy, ever) and that is the Hyper 7. It is sold in several configurations, including sport kit (c-hub suspension no motor/electronics), Ready to Run (pbs suspension), Ready to Run w/ PCR chassis/suspension upgrades (PBS suspension), Pro ARR (kit c-hub w/motor), and PCR Pro kit (no motor/electronics).

Hong Nor has a wider product line. They make something for just about everyone. There is the Ultra Series (entry level), the 9.5 series, which may also be called Violator or Ravager (beginner-intermediate), and the Jammin series (beginner-advanced). They make alot of different versions of each of their cars, and they keep old models around (and still update them), even as newer ones are created, so there are too many models to list. I believe the Ultra series has been going for almost a decade now (but has seen many revisions).

There are many other good manufacturers as well. None of which release so many 1/8th buggy kits as OFNA (since they re-sell TWO companies models), so your choices are more limited. XRAY and Mugen mostly cater to those with a higher budget, selling pure bred racing kits. Kyosho offers two models currently one pure race (MP 777), and one entry level (MP 7.5 Sports). There are also some less established companies that are gaining popularity as well. Companies such as Sportwerks, GS, and CEN have been getting a larger fan base.

The main things to consider if racing is your aim, is what can I get parts for locally, if I need something in a hurry, and also, what are the majority of people around me using. If you are new, and you run a car that absolutely nobody else has, then it makes it tough to get setup information for tracks. If you are just backyard bashing with your buggy, then the second point doesn't matter as much as the first.

My personal recommendations would be:

Low budget (under $500):
OFNA Ravager RTR
OFNA LX Comp RTR

Mid budget ($500-$1000):
OFNA Jammin X1-RTR
OFNA Hyper 7 PCR PBS RTR
XRAY XB8 Raycer
Mugen MBX5
Kyosho MP 777

High budget ($1000+++++):
Jammin X1-CR
Kyosho MP777 SP2
Mugen MBX5 Pro Spec
XRAY XB8
Hyper 7 PCR Pro