I assume the 10x is enough
You are absolutely correct here. There is absolutely no reason what so ever to have more than 10 times magnification on a big game rifle.
but want my minimum mag. a little higher so I'll probably rule out the 2.5 x 10.
And this is where you went off course.
Why would one want to sacrifice low end magnification on a big game rifle unless it is a specialty long range rifle that is used under very specific conditions? If you get a 15 yard shot on a bull elk in thick timber you will dang sure wish you had opted for the scope with the lower magnification. A big game rifle should have no more than 3 times magnification at the low end. If you can get higher magnification while still maintaining no more then 3X at the low end (such as the 3-12X) then by all means do it but if you sacrifice low magnification mark my words there will come a day when you will want to kick yourself in the butt for not listening to me.