Like someone else said, Elite is now free, but for BLOPs II you need to get the season pass.
As for the value of playing with the maps, you have to remember that you will have to be matched with people using those maps so your matchmaking potentials will drop. Plus, the majority of the guys using the maps are sometimes more experienced players and you may have a hard time depending on your skill level.
Personally, I'd consider how much you will be playing. I downloaded all the map packs for MW2 and MW3, but rarely activate them. I don't play as often as I like and it's much harder getting familiar with 20+ maps vice the original dozen or so. I'll stick with Elite, but will forego the map quest unless one jumps out at me.