Yes what Matt said. The GP25 is a clone of the FP25. A good engine too, the one I have is excellent, if anything it is better made than the FP25 and definitely better made than the LA series engines.
I have never flown an LA25, so can't speak about a flying comparison. I note that new GP25s can go for very little money. It is hard to resist when this happens. If you need spares get them now, because Magnum have stopped making the GP25. Spares for the FP25 fit, but they are becoming scarce at Towers, mind you, there is a lot of stuff out there, it is just a matter of finding it.
Andrew.