I tend to go with which ever game gets a higher rating on Gamespot.com, or ign.com (Forza Motorsport 3 > Gran Turismo 4, etc.) - I own Live 10, however 2K11 is intriguing because of the whole Jordan subplot.
I think the level of control has regressed in the Live series in favor of overtly long, often-times awkward character animations which compromise the level of strategy one can use on the court and instead make the game feel arcade-y. NBA 2K10 suffers from the same plight; both games quickly just turn into a pass, pass shoot/iso-fest where defensive schemes are secondary to the offensive pacing.
I like NBA 2k10 a lot (besides the crippling bugs) but that game was just as hindered by long, uninteruptable animations as the last few LIVE games.
Regarding 2k11 and Elite 11, I think you'll like both games if that is one of your big beefs.
2k11 supposedly has redone their animations again and now they are interuptable to the player and blend together. There are also better collisions between players bodies.
Elite 11 is taking that idea to the next level. The lead designer that redid the NHL series is the lead designer on the Elite games now, and that is a good sign. As with NHL 07, Elite 11 is trying to leave behind canned animations and use the sticks for controls, allowing you to change out of any animation and have complete control over everything your player does. There is a great video on Youtube that shows all the posibiliities, I can't access Youtube from work though, so I'll have to link to it later for you guys.
While I really like the direction Elite 11 is heading in (a direction 2k11 is more half heartedly going in) I think it may be a promising though rough game this year (like NHL 07 was), but in the future I wouldn't be surprised if it is the far better franchise.
Elite 11's graphics, from what they've shown, are of a far lesser quality than what 2k 11 looks like. 2k looks yet again much improved in the screens I've seen and in aciton supposedly looks beautiful. The Jordan bit is a cool addition, though I really wish they could accurately make the whole league from back then. It's not right being Jordan and the 96' Bulls and playing against modern teams. Where's Bird or Magic or Barkley?
Anyways, it is a great year for basketball games. Also keep in mind the new NBA Jam is coming to Wii in October and looks fantastic, and if you buy a new copy of NBA Elite 11 you get a digital copy of NBA Jam for PS3 or 360 (it is a stripped down version of the Wii game, but is in HD and has all the classic NBA Jam modes). That alone makes Elite 11 a good buy if it's at least a pretty good game.
NBA JAM! I am maybe most excited for that. It's been so long since I played one and it looks like a great reboot.