dan- i have killed quite a few mule deer bucks with the 85 sierra bthp. also the horn100 and several with a 95 partition. i would think with the same bullet placement the 85 sierra and 100 would be the same.
I personally would go with the 100 gr. You might get an angling shot on a big old buck and you will need the 100 gr to get to the vitals. When I deer hunted with a 243 I always used either the Rem 100 CL or Sierra and they always did a great job.
The best? That's a hard call. I don't think there would be a lot of difference from 20-200yds. My dad used the Speer 85gn boat tail (1213) and I've seen him make some fantastic shots on whitetails out to 500yds with this bullet. As "roninflag" indicated with the same shot placement the results would be the same. Dead deer. JohnnyK.