I second bkdavy.

I think its all personal preferance. Some learn faster than others. Its the self confidence to what airplane you fly. For example, if you have been flying the sig lt 40 for a year, and are very comfortable, and want to move to a sig four star 40, but your don't think you can fly it, don't. Not only is it unsafe to not fly an airplane you don't think you can fly, but not very fun. We should have fun flying these airplane, not scared up to our ears because we don't think we can fly it. Theres a guy at my old field who flew 1 solo on his lt 40, and came to the field with an astro hog the next day. I looked over when he was ready to take off, and he was shaking like crazy, because he was nervous about flying it. He wasn't going to enjoy flying it, because he was so nervous about fly it.

All Personal Preferance.