Hmm, it depends on how you break it in, what fuel you use, etc. Basically, I've heard a lot of people from my LHS saying that NovaRossi and Ninja are popular, but are really expensive.
Throw away that .46 of yours, (well not actually throw) and get yourself a .28 Axial or LRP, OS, RB or Sirio. All great engines
If money not too critical then Picco Navarossi. Unless you're racing stick with the .28
For on-road you typically want something with a smooth power band with power towards the mid-top of the RPM range and a high peak RPM. Also they typically come with smaller cooling heads since the vehicles they are in run at high speeds.
For off-road buggies you want something with good low end torque that can "squirt" you over the doubles/triples with a short runway, but also have a higher peak RPM for the back straight.
For off-road MT's and bashing, durability, torque and high HP are what you aim for.
Rarely will you find one engine that is good for all scenarios. They are typically purpose built for a specific task or vehicle type.
Amen to that!! I can't tell you how often I see people stuffing huge motors into their rides yet not having the suspension to handle it, I love it when I see that, because I usually take their money at the track. When I build my drag cars, the suspension is the first thing I start on before I even consider an engine. Once I have the suspension dialed, I go through it and decide what kind of power it will handle with what gear ratio and the tires that I will have on it. Once all that is done, I start on the engine. Now this is my experience in drag racing, and it is exactly the same with RC's. The fastest driver usually doesn't have the fastest truck, yet he still wins.