Unless you need to count rings, kickers, eye guards or whatever a good pair of 15s will do the trick. When you do have a spotting scope in the pack, there is a tendency to reach for it the moment when a buck is spotted. When you don’t have a spotter and just keep watching with the 15s, as the animal moves and turns its head etc you end up getting a very good idea of the trophy quality without needing the spotter. The spotter can almost be a crutch that you think is necessary because you keep using it. Depends on the actual distances but if forced to choose just one, it’s going to be 15s for just about every hunt for me.
Also have used the leupy spotter, non HD version…it’s a good scope very ergonomic and excellent eye relief. It’s a good tool paired with 10s or 12s if you really want a spotter. Magnification is overrated, it’s rare in my experience that atmospheric conditions will allow for use of much beyond 40x magnification anyways. You need cold, snow, good lighting, etc for the higher magnification to actually reveal significantly more detail. If you are truly needing to assess detailed trophy quality then maybe you want a giant objective lens and high zoom…but if you just need to verify he’s a big deer/elk/etc than I think magnification is way overrated and you can get a ton of information and a lot more use from 15s, or the leupy spotter in question.