If you're strictly considering between the 4-Tec and the HPI only, I must say HPI is the only way dude. You know the facts man, in terms of handling, hop ups, parts availability. Most importantly, the QUALITY of the make.
If you're leaned towards getting the HPI now (which you definitely SHOULD after so many opinions from everyone in here), I would also suggest a thought on the NTC3, which in my experience is a great car. I had both of the Type SS Kit and the NTC3, after driving both of them, I just like the NTC3 more, the way it handles. I won't brag about it too much, it's just like how u like a particular brand of briefs if ya know what i mean. HPI is good, but in my opinion if you're serious into racing, NTC3 has what it takes for racing.