[popeye]

I had a M1A scout. Probably best for your multi purpose. I was satisfied with mine but I traded it for a N.M. M1A. Mags for AR10 (nice piece too) are modified m14 and rather pricey. However AR10's come in a basic model and retail for $1000, so you may find one for $900. Uh......given your choices, and what your demands will be, it's almost a coin toss.
Butt, I would go with M1A full size. Long range capabilities are outstanding and you will never lose money on investment.