Hi Damo
I have owned both a skyline gtr and a supra tt and both are great cars.
It all depends on what you’re after from your car? , if you want to achieve big bhp the supra is the far easier of the two in relation to BHP per £.The skyline cost a little more to make gains.
The skyline is a far more forgiving car to drive fast (in my opinion) with the ATTESA-ETS 4WD system and the Super-HICAS all doing their part to keep you the right side of the hedge .
I found the supra a more demanding car to drive fast (you have to be awake ).
If Practicality comes into it the skyline is easier to live with as it has lots more head and leg room ( I am the same height as you and I found both ok ) and your mates wont be cramped in the back lol.
I could go on but just have a look around at japfest and talk to the owners, people on this forum and all skyline owners are a friendly bunch and will be happy to talk and answer questions.
Cheers
DAN