I would seriously recommend you a PS3... Apart from all fanboy crap, lets get facts straight shall we...
1) Myth 1:XBL is superior to PSN..... Answer Yes it's superior, but not by a margin that fanboys blow it.I own both and here is the thing that XBL is superior in... It has a few more features like Cross Game Chat (Primary bragging right for 360 fanboys as it allows any one playing a game to chat with another player playing any other game) and Netflix and it has a little better interface... But here is the thing, Sony has made a rule for ALL it's first party devs to set up dedicated servers for their games...
The main advantage of dedicated servers is the fact that even if you have a slow connection, it doesn't lag... You must have heard of a game called Gears 2 on the 360.. It lags like crazy due to no servers (10 players online max).. While a game called Killzone 2 (PS3 exclusive FPS.. Halo killer) which is termed as THE BEST LOOKIN GAME TILL DATE can support 32 players online at at a time (Halo only 16) while another game being released next year named MAG (FPS) will support 256 players online !!!!!!! Ya you heard that right 256!!!! Not a single 360 game supports more than 20 players online whereas PS3 FPSes like Resistance 2 (60 players) Killzone 2 (32 player+Best looking) and MAG(256 player) push online margin.... DEDICATED SERVER FTW!!!
MYTH 2: PS3 has no games- This is a real easy one... This year alone PS3 has more exclusive games than the 360 (Killzone 2, Uncharted 2, R & C, Infamous...). Last years GOTY (Game of the Year) awards went to Little Big Planet and MGS4 (Both PS3 exclusives)... Even this year, the GOTY award is likely to go to Uncharted 2 (already highest rated exclusive on meta (link... Higher than any 360 or PS3 exclusive game till date.. 97 whereas Halo at 94, LBP at 95, MGS4 at 94, Killzone 2 92)). This is THE GAME TO OWN ON PS3.... (it's a TPS like Gears).
With both the above myth busted, lets get to the questions..
1)PS3 has a similar feature to achievement system. It's called the TROPHY system. Trophies are divided into Bronze, Silver, Gold and Platinum... It works in a similar way. The multi plat games are always the same with the same format of online ranked matches and stuff.
Frankly speaking Halo is over rated. It isn't even rendered in HD for crying out loud (600P resolution while HD starts at 720P.. Google it if you want). The graphics when compared to current games are poor, and the gameplay is noobish. I would highly recommend Killzone 2 as it's the best FPS I have played this gen. It doesn't have partial auto aim like COD or Halo (yes both have partial auto aim).. This game is realistic and has no auto aim help... IT tougher and trust me it's worth it when you play with 32 players online with graphics unparalleled....
The game itself weighs more than 40GB (YES 40GB!!!!! Comes on Blu Ray.. It has 20 GB textures.. Thats more than 2 Halo games just on textures Lol)
As I said, PS3 is worth the money.. Just get this... Both PS3 and 360 at same price.. PS3 gives you an added Blu Ray player, wifi, Bluetooth, Chargeable controls (not provided in 360), FREE online, better reliability (360's have failure rate of 30-40%)... Plus more upcoming games like God Of War 3, Uncharted 2, FF vs 13, GT5, MAG, Heavy Rain, TLG, R & C, God Of War Collection pack (GOW1 and 2 in HD)... It only does EVERYTHING.