I would go for the Fox .35 also. Probably no other engine does the old 4-2-4 break out of the box like the Fox. If you need more power for a larger plane later on then you can upgrade it to ABC with hemi head and stuffer backplate and have more power than the OS .25 LA. Don't bother to wait for it to wear out, because it never will. In fact buying a used Fox .35 and adding the upgrade parts is not a bad way to go.