interesting we have done back to back testing of our own on my personal car comparing a gt3076r to a BW s256 which supposedly spooled up 500rpms faster and made more power than the 30r. the s256 was a good turbo but not quite all it was cracked up to be.
spool was similar to my 35r.
garret also offers a catridge exchange program so if you destroy a wheel you can exchange your center section for about the same price as a wheel and rebuild.