RCKen has put together the definitive trainer list at http://www.rcuniverse.com/forum/m_4537845/tm.htm

I have flown, built and/or buddied Global RCM 40 Trainers, Sig Kadets (various sizes: LT-40s, Senioritas & Mk IIs), Hobbico Superstar (& Select). If you're building I would say the Sig Kadet Mk II. If you're buying the RCM 40 Trainer (with a Thunder Tiger Pro-46 engine).

I have heard and seen good things about the Hobbico Avistar as a "better flying" trainer. No first hand experience. My RCM 40 did better rolls and steadier inverted than most.