60's have the advantages of being more visible in the air and handling wind better. The disadvantages are that they use more fuel, cost more, and take up more room in your car. A lot of "older" guys prefer the 60 size trainers simply because they are easier to see. 40 size trainers are plenty big enough for me and handle the grass just fine.

If you are already a heli pilot, then your training might go pretty quickly and you may be looking to move to a sportier plane sooner than most. If this is the case, I would go for a low budget trainer, like the Tower Trainer RTF package. It is an excellent trainer and the gear is all transferable to your next plane. It is cheaper than the Avistar RTF package, but it comes with a ball bearing .40 engine. The Avistar RTF comes with an OS .40LA, which is a great engine, but has less power than a BB engine.

You can also go with an ARF trainer, and buy all of the gear separate, but it won't save you any money.

Good luck