The only 'real' way is to do a proper survey, and not just listening to whoever shouts the loudest.
There are many good arguments for both designs.
That being said, I don't think the ACA500 will be for me unless it is internal, which is probably off the table now. I could probably accept a small external box about 1 inch wide and not taller than the A500, which would mean the 1200 acc. would still have to be inside the 500 and maybe just power supply and CF cards in the external cabinet, but it's hard for me to see how it could be possible to achieve. Even harder when you consider the price target.