Having always been a SGC kinda guy - I have lots of crossover from PSA to SGC experience. I have always sent cards in original slab and have set "minimum" requirements for crossover grade. Over the course of several years I would say my crossover from PSA to SGC has been somewhere around a 70% success rate.
Over the last year or so I have determined that PSA cards with the "Hologram" slabs (frontside PSA Holo on Flip) have done better than 70% (maybe around 90ish percent)
Just got these back this week from SGC -
This one was submitted as cross from PSA 7 (1st gen holo on flip) to minimum SGC 84. Result was "Did not Meet Minimum" (crap - still scratchin my head a bit on this one)
This one was submitted as cross from PSA 7 (1st gen holo on flip) to minimum SGC 84
This one was submitted as cross from BGS 7 to minimum SGC 86 (actually thought it had shot at 88)
This one was submitted as cross from PSA 7 (1st gen PSA Holo on flip) to minimum SGC 84 (wasn't real sure it would meet minimum when sent)
This one was submitted as cross from PSA 8 (1st gen PSA Holo on flip) to minimum SGC 88 (really thought this one had legit shot at a 92)