The boss 302 LS/ non LS are great cars! If track and performance were my biggest goals, then i would stay far and far away from M3. They are not the best for the money, and very costly to mod.
I got a M3 because i don't see the track often at all. the luxury side of the M3 was very big for me. I also love the looks and performance of the M3 very classy and sporty. I think mustangs look very cheap inside and out.
but again its a good car for the price!