Its always true that you get what you pay for. Novas are know for their quality and longivity. Had a few nova but dont have much success with it. I am not a good tuner so I want an engine that keeps a tune over time with minor adjustments only. I have a nova that I really like (7bt) solid tune always with a p3 plug. Others I am not lucky with. Although I dont own the new novas but the toro and plus 4 are pretty solid engines IMO.
I do own an orange head alpha and its a pretty solid engine and will keep up or even faster than the plus 4 but not the toro. I use it for club races cause I am not certain how it performs. For big races I either use the ninja or the speed.
The alpha never failed me yet. Its kinda touchy with the changes in temperature. For example I tune it Mid day for the quali but needs to retune it in the mains since its colder already. I never do that for OS based engines. Its not a big tune thou needs to lean it out a bit cause Alphas wants to run hotter IMO around 240-260. Longivity wise, well I still dont know but for its price. Ill buy 2 alphas to get a longivity of a nova. IMHO, the way its going I think I can get 8-10 gallons out of 1 alpha which is pretty good. two gallons already and it still pinches at TDC sometimes. I do own an engine warmer so it helps in the longivity of the engine.