All depends on the use. If your talking moose/black bear in the thick cover 175's are optimum. Elk round and a compensating scope the 160's are pretty nice. The 140's and 150's have some speed and are great if you have a simple set up where your using hold overs to shoot at medium long range 600yards max.
I'm a speed and accuracy guy. Most of my rifles shoot within a inch or two of each other at 500yds for trajectory so it is real easy to pick up several different calibers I own and shoot the same shot on big game animals at longer ranges. Not extreme long range that takes a whole different setup or a lot of luck. It's all depends on use and knowing your trajectory. If you never shoot over 300 yards then none of it matters. Any bullet weight would suffice.