They are two very different things. Live gold offers online gaming features. PSN+ doesn't add very much at all to the online experience. There are cloud saves and patching which Live also offers. PSN+ is basically a content platform offering deals on new content, including free complete games and discounts on all store content. It's more a gamers loyalty programme than anything. As such, PSN+ and Live aren't really comparable. Live should be compared to vanilla PSN, which offers basic online gaming and some chat but isn't up to par with Live.And the discussion is what psn+ offers that live doesn't.
Having said that, we played Halo 3 on XB360 yesterday and the party aspect was really annoying! Wanted to play split screen coop, and the back of all the Halo boxes said 2-4 player coop in the green section, different from the 2-4 player coop in the red section for online, so we understood it to mean local coop for 4 players which I said I didn't think they had but thought maybe Halo 4 had added. Each controller that we switched on had to log in to an account. Then we loaded the games to be told there were too many players. So we switched off a controller but that didn't log the player out; he was in the party. So we had to switch on the controller, log him out, and then switch it off to play. I just can't get on with the dashboard, either the old one or the new one! Going to the 'game' screen didn't show the game in the drive to play. XMB is far more obvious and user friendly IMO. I wonder where the two consoles will go next-gen? Sony are supposedly abandoning XMB which kinda worries me. It has faults, but should be updated rather than replaced.