Hi Yoof,
The ITC finished 6 months ago mate and i've just finished the Generic course. I'm currently waiting to be streamed, hopefully as a Rotary Crewman. The big disadvantage WSOp has over WSO is obviously the rank and pay, for starters, although that tends to even itself eventually, but the fact that you could train for a year at Halton, then Cranwell on the ITC and the Generic course only to find that you're streamed into a job that you aren't particularly keen on. For example, if you join up dead-set on being a Chinook crewman, because it looks the most exciting, you may find yourself actually streamed as a Nimrod Acoustic man and the looks of disappointment on some people's faces is not nice. As long as you're prepared for that, then you'll be okay. At least with WSO, you know that somewhere down the line, whatever aircraft you fly with, you're going to be on the flight deck.
That said, those that have been streamed into positions they didn't really want generally end up enjoying it and the Generic system is designed to allow those that remain disillusioned to re-role after their first tour, so eventually you would get what you've been looking for, it's just a long way around.
Anyway, good luck with OASC, hope it all goes well for you, whatever you decide.