I'm sure your a nice bloke too...
I'm not implying that 2530's are a crap turbo, I'm saying that from my experiences mainly information that I gather from a workshop here in Melbourne that works mainly on GTR's is that the -5's are superior in how they make the power, they are more responsive than the 2530's but don't make as much top end. This workshop I'm talking about has done a lot of R&D on GTR's and what makes them go fast for mainly street and circuit, so response and low end power is the focus, so why the -5's are used and not the 2530's...
Anyway, I guess people will eventually work out whats the best turbo setup for their car, it sometimes takes 2 or 3 goes.. well it did for me!!!!