"Both have cars, both have racing, so what's the difference?"
For people unaware about these racing series, you should know they are probably the best racing simulations in account for realism. Gran Turismo is the PlayStation exclusive series and Forza Motorsport is the Xbox loyalist. They are not NFS-ish titles giving a laid-back and blissful driving. Gran Turismo is a completely settled franchise now whereas Forza Motorsport is a brand new series having only two titles till date.
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