sorry i generalised a bit too much. The later s13 and s14 boxes are near identical save for the bearings and centre plate as described. the others vary in design although in terms of which box will withstand what levels of power, its as much to do with condition of the box and how its been treated (most are now 20years old!) and your particular car, its power delivery and intended usage in my opinion, but with 300hp you will soon know if you need an OS giken or PPG box for your driving style
as mentioned S13 Eater has had a proven 305hp with an 8v engine on an early, supposedly weaker box and it survived, whereas its common for s13 and s14 boxes to die earlier that that if the forums are to be believed