I have not participated in a competition but I have spent many hours shooting both rifles.
My vote would be for the 15-22, but I suggest you find a range near you that has them available for rent. The only way you will know what is right for you is to shoot them both.
The 15-22 does hold the bolt open on the last round and if you do go with it the trigger is easy to replace. There are countless threads on this forum discussing different triggers and their pros and cons.
Good luck and good shooting.
