Neither of those engines is a powerhouse but I would put the LA in the trainer. It will fly the 4*40 but will lack a lot of umph. The LA is a very reliable engine but a weak one. Lots of folks bash them, but for the price they are not bad for trainers and such.

For a second engine IMO its better to go with a 46 sized engine. Same size motor but has more power. I think the Thunder Tiger 46 is a fantastic engine.