Wade- I’m an old geezer and have a leopard, and have run a rotax. Running these things at a competitive speed is a chore and, if you get stuck to the track, absolutely brutal. Neither is cheap, and as has been mentioned both have drawbacks. If you go Rotax, make sure to bring a spare fully charged battery. Its the only way to start them, as they can’t be started by an external starter (no mag). So if the battery is flat, you don’t start. I don’t think you have to keep the motor sealed if you don’t race rotax, and can do some of your own stuff. You will find the tax has a flat spot in the middle that can be frustrating if you drop the rpm’s too much. The leopard will shake you to pcs., and make sure you have an external starter, the brushes to tend to give out on the starter. I warm mine on the stand in the morning to get heat in the motor to help starting. You sure you won’t look at a Yamaha?
Easier on the wallet, last a long time, less to fall off, no $400 trick carbs, (tax) starters locking up and taking the crank off (leopard) and at the end of the day you can still walk around and load up your stuff. Regardless, have fun.