When the axial's first came out they did have some issues but the more recent ones seem to be good. The major thing with them was the carb needed to be sealed.
The 427's and the mach's I have never heard of any problems. I have owned both and seen a ton of them run and they all were flawless. The sportwerks v2 is basically a mach 26.
The LRP is a very nice engine that I believe is made by SH engines.
The Picco P3 .28 has tons of power everywhere through the rpm band.
As far as which engine is right for you comes down to a couple factors. The thing with having a budget means you kinda have trade offs in a way. You can get a budget .26-.28 that will have the same if not quite a bit more power than a high strung expensive .21 or you can get a budget .21 that is more suited for a lighter buggy.
The jammin/picco .21 that's out now is a nice powerful engine for the money. It's basically the same engine as the old trinity drake .21's were. It's also right around $220 or so.
Most people that race a lot prefer a nice strong (often pricey) .21 in a truggy because of fuel mileage and they are often times a lot smoother than a torquey .28 is. It's a lot easier to put down fast laps with an engine that is controllable down low than one with an explosive bottom end like some 28's have.