I guess maybe there are several different view points, because people have different need to consider. A .45 can get some more velocity up to 200 FPS which can produce a difference in point blank range. The possible problem is can you with the very limited supply of bullets and sabots fined a combination that has enough accuracy to take advantage of that velocity. On of the other things I have noticed is that Blackhorn seems to be a better match with the .45 than with the .50.
There is also the problem with some state laws. I think that will eventually be leveled out part of that problem is law makers who do not understand the sport or the progress being made in it. A 45 with a heavy .458 bullet and the right sabot and say 130 gr of BH would more than equal a 45:70 in my opinion. A little time and a few more options may well see the .45 come to life again.