Look FRAG....obviously, we have the Mugen, Serpent and HPI ppl here defending their car performacne............so, take notes from them and figure out what you are going to get...
And here is mine...(I have had Serpent S710 and R40 and NTC3)
#1..........YOUR TRACK........who are the fastest guys there? I mean top 5 (A1-A5).....what are they driving....? Take a look...and see what they have....the best car to get is what they have, cause if you are a NICE enough guys, these ppl will help you a lot.
#2...Parts support...easy, in CA, I don't think you have any problem of any MFR (compare here in CHICAGO, Mugen parts is only ONLINE orders...)
#3.........How much money you want to invest...? YES, INVEST, not WASTE....HPI parts are cheaper (compare to MUGEN) but HPI OPTIONS are nothing but cheap...just like any other OPTION parts from MUGEN or SERPENT....then, do not tell me you will NOT option your car, because YOU WILL...........and compare to MTX3, yes, R40 will have more AREA that CAN BE UPGRADE...but again, it is up to you.......if you can run the stock R40 the frist time and get to the A-main...you don't really need UPGRADE then.
#4....release date.........R40 released about 6-8 months later then MUGEN MTX3.......if you really need to FIND a way to decide your car, considered the release day, later release car (the same level car, don't tell me HPI RTR release in 2004 is better then S710...LOL) MIGHT be better.......but that is only if you have nothing to compare....which I would not recomment.
If you have to ask me this minute....I would say Mugen, because, it is MUGEN....yes, I am one of those follow the NAME BRAND, but if you have to tell me am I GARANTEE I drive the MUGEN faster and BETTER then R40.......I would not say NO.
I built one R40.........it is NOT TYPICAL HPI, it is a TOP LEVEL race car, and definitely CHEAP PARTS (I mean the cost) and you can find parts everywhere......which I love the most.
P.S...Forget about the R40 2004 spec upgrade kit or the 2004 spec R40 kit, it won't be here in USA unless you order from Japan direct.
It is very simple......you want to race a car BY YOUSELF (no need any help from others), or you want to learn from others and race with others....(like at your track, Team Mugen or Team HPI...etc)
One last advise..........FACTORY TEAM NTC3. Best bang for the buck....