I think with the 9520 you have to deal with DRM and non-DRM OS's. Something to look into. It also seems the 9520 does get more leaked OS's because it's used more around the world. I think they are up to .669 or something, while the 9550 is stuck at .607.
I had a 9550 on AT&T for a few months. I had to reload some service books (MMS for one) every time after reboots. I also lost EDGE frequently. I brought a Vondafone 9520 of eBay earlier this month and have had great success with it. I now keep EDGE and the service books stay after reboots. They were still there after I loaded a hybrid to it. The only down side is the DRM thing, so far this hasn't been an issue for me.
I can't say how it will work with 3G overseas, I don't travel abroad.
I had a 9550 on AT&T for a few months. I had to reload some service books (MMS for one) every time after reboots. I also lost EDGE frequently. I brought a Vondafone 9520 of eBay earlier this month and have had great success with it. I now keep EDGE and the service books stay after reboots. They were still there after I loaded a hybrid to it. The only down side is the DRM thing, so far this hasn't been an issue for me.
I can't say how it will work with 3G overseas, I don't travel abroad.