sam engine wise and brake wise i'd have to say the skyline wins in those aspects. Even the 34 gt-t has better brakes, the engines speak for themselves. The sr20 in my opinion is one of the best four cylinder engines around although its not as tough as the rb engines. Watch high perfromance imports 3,4,5 and i think 6 coz they modify a 34 gt-t with a xaust, cooler, avc-r, boost and one the dynos just from that they are reaching 200rw kw's!
Ofcourse a gtr is better than gts-t but also make sure you think of the money you will save, and how worried you would be everytime you park the gtr and how pissed u'd be if it got keyed of something.
Just listen to the little man inside you and he'll tell you what to do!
my little mans an idiot! hehe