Shouldn't be a huge change, but you never know how the rifle will react until you try it. You could also try going over 100gr and see if you can find another, heavier charge that will shoot good again. Don't forget to mix up bullets to try as well.
50 v. 45? I'd probably always go with a 50. Some states won't allow 45s for elk (NE for example). Another disadvantage of the 45 is less availability of bullets, but you can always get bullets and sabots separately.