whats the best engine for both performance and mileage??

Its been said time and time again. Comparing the ls series engine to an la engine is not a fair comparison. You need to compare a late model hemi to the ls series. A magnum to the vortec and an la to a regular 350.
I believe it was albert einstein that said everyone is a genius but if you judge a fish by its ability to climb a tree it will live its whole life thinking its stupid.
basically everything works but if you judge old technology compared to new its gonna look like crap.
Stop comparing you plasma screen(LS series) to a tv from the 60's (LA series)