I'll jump in on this one. My herd is all double registered AMHR/AMHA -- but I will say that I am trending more toward the AMHR registry ever since AMHA closed their books.
For me to be able to reach MY breeding goals that include the refinement, necksets, pretty heads, out of this world movement, etc - I will likely need to incorporate some ASPC/AMHR blood (still on the fence about this a little) -- sooooo that means I will end up with AMHR only horses -- BUT I are really striving to hit the 34" mark with my "perfect horse" - so hence it could possibly end up as an AMHA sized horse, but be unable to be registered since the books are closed -- my personal opionion -- that is AMHA's loss and AMHR's gain -- there are far too many beautiful AMHR/ASPC/AMHA horses that are being blended that will end up being 34" and under that will have no registry except AMHR to go to.