Where you are with your heli flying should dictate what trainer you get.

If you're already into comfortable (that is, YOU'RE comfortable doing it) forward flight with the helcopter, then all you need to learn is how to land. The helis fly the same as fixed wing in forward flight, with less stability; so if you can steer your helicopter around upstairs with no issues, an airplane will give you no trouble.

Landing is another ball of wax; and the most difficult aspect of learning to fly.

What you're looking at here is wing design. This has been briefly touched upon in Randy's post. The Reader's Digest version is that a flat-bottomed wing is more stable and makes the airplane fly and react slower. The downside is the ground-handling problems noted, and the airplane really doesn't do aerobatics that great. You can force it to, but...

The semi-symmetrical wing makes the airplane a lot more lively, which is what you'll be looking for once you solo. However, it will fly the approach and landing pattern at a faster rate, thus complicating your learning curve and leaving much less room for error.

So, IMO, it really depends on how far you've gotten along with your heli flying. And you need to be honest with yourself. If you're still at the hovering only/knocking-knees stage, get a flat bottom wing- a TRUE trainer. OTOH, if you can fly your heli around comfortably, then by all means go for the semi-symmetrical wing airplane. I have taken fairly accomplished heli pilots and soloed them in one day on a Hobbico Avistar. Heli pilots are accustomed to paying close attention to the model, and make excellent students. Once they learn how to fly an approach and manage the throttle, they're good to go.