If you previously owned both systems, you surely know the answers?
Loading times - much of a muchness. Maybe slightly quicker if the game part installs on PS3, but then you're often forced to do the install. Full (optional) installs are coming to the 360, so again, much of a muchness.
Online - pretty much the same in terms of connection/lag (both very good in my experience). Dedicated servers make a big difference in games, but both PSN and Live have games with dedicated servers. Downloads were quicker on Live for me. Personally I couldn't live without the private chat feature (soon to be a full blown party system) and the overall seemless nature of Live (little things like Join Session, the xbox.com portal, gamercards, Achievements in all games, etc). But that's just me and those features might not be so important to you. Plus you pay a small fee for Live, which some people don't like.
I doubt very much has changed since you owned both consoles TBH.
