mustang remains with us, the gto (originally a great car) gone....mustang will be easier/cheaper to maintain, and provide all the muscle you will need. if its a daily driver, no contest has to be the 'stang.
the ford modular 4.6 ranks right up there for dependability.
with a mach 1 you already are a notch above mustang gts on the street and if you want to be a serious contender there are lots of after market mods available.
go with the mustang cheers, 04 cobra terminator, 575 rwhp http://www.cardomain.com/member_page...jpg?081519-289
Since the GTO wasn't a big hit when it was new, there are a lot fewer of them on the street. Not that they were bad machines; they simply cost more than the Mustang and the styling was kind of anonymous.
There are many businesses devoted yto go-fast equipment for Ford and Chevy small blocks. But to me, the GTo would get the edge because there aren't as many of them.
you know what, i like both cars i have had 3 MUSTANGS 2 V6'S and 1 GT
and i love them specially the 96/98 style. which to me looks a lot like the GTO, with the pointy front and the rear fenders that seems to grow wider.
but power wise i will pick the GTO, i thing it will be more fun.