World Models T-34 Mentor, without a doubt! I have had both the T-34 and a 4*60 and for a second low wing plane the T-34 is much better.

The T-34 is much easier to land smoothly than the 4*60 and it has tricycle gear like most trainers making it an easier transition. I have one with an OS .46FX and it is an excellent flyer.

Lands extremely easy and can do most basic aerobatics that a 2nd plane pilot would be looking for.