My advise is try a few scopes before committing, especially if you spending Leup money. I always wanted a Leup Comp 45, glass is very very good however i found the high mag difficult to shoot all the time, especially with standing shots but that is something you would have to practise and get used to. A lot of people use them and love them i just didn't give it long enough.
I had one of the first silver T50's as my first FT scope and i was fairly impressed with it, the only thing i would say is get a quality wheel from Mr Harris or Rowan. The cheap Chinese junk wheel that it comes with just needs binning imo, always working loose or spinning and giving false ranges. The other thing with the T50 is the 50, 55 are very close and hard to distinguish (on my one anyway) but for the money its a good scope.
The Big Nikko is a great scope, i had a MK1 for years, very clear glass and good range finding, it would snap in and out very clearly and i would highly recommend one.
Another one to consider if you were thinking Leup Comp money is a secondhand Sightron SIII 10-50x60 just to trow another spanner in the works
My advise is try a few first, most shooters are more than happy to let you try there rifles and it will give you some idea how each will perform in the field.