Premium all the way. If the base GT has the same interior as the base V6, then go for premium definitely. The steering wheel is all black cheap plastic, the dash panels are a grey plastic instead of real aluminum and the cloth trim looks like its 5 years old when its new... plus no Sync, no stereo controls on steering wheel, etc.
I have a base model... I have spent a lot improving the interior because its so poor...
2015 50 Anniversary Package GT
2014 Race Red Premium GT Convertible
2003 Silver GT
1981 Ford Mustang Fastback
1966 Mustang Coupe 289 4V
15 years ago 1984 Ford Mustang Hardtop