There's no reason you can't do both. Uncropped ears are a deviation from the standard only - they are not even a fault. If he is a quality dog in most other ways, he should be able to hold his own. I would suggest really choosing your judges carefully whenever you can - there is a regularly updated list of judges that will and will not put up natural-eared Boxers, I've posted it before so a forum search will pull it up. Yes, you will get some flak from some people, and you might get excused, but many judges look at the entire dog, and not just the ears
(In the ABC Top Twenty Competition, where dogs are graded on a point scale, out of a possible 200 points ears are worth 2. Makes you wonder what all the hoopla is about, doesn't it?)
I would not sacrifice the UDX for conformation, though, IMO the UDX is more important to the breed.