Being an long time COD player and a long time BF player with following record:
COD:
>MW (level 54)
>MW2(Prestige 2,mostly using the M4)
>Black ops(not bother to played online, except the weapon sweeping mode)
>WaW(just war,dont remember the level I just remember to play with MP40 most of the time in "war")
BF:
>1942
>BF2
>BF2142
>BC
>BC2
>MoH(multiplayer)
I will say that I'm more interested on BF3 than MW3,not that I'm saying that MW3 will be better than BF3,but it will be a game for the next generation,I'm aware of the changes that went through the COD series during the last 5 or so years,but the gameplay its complete different in BF,(based on my MoH experience)I will say that gameplay in BF3 will be more balanced and planted(infantry),so allow me to elaborate:
Normally on COD your online skills are determinate mostly by the usage of the quick scoping,one massive problem with it is that its setting value(or at least in 360) is too high,for runners is perfect,and in good matches you can get most of the thrill by using the level design and good use of short range weapons,but then there are snipers,snipers and quick-scoping are a massive problem in online play, because both intervention(MW2) and the R700(COD4) are used as over elaborated shotguns,something that makes the online play really annoying,there is not solution for it due to the setting of the aim assist,Its been said about a lot about weapons balancing and updates fixing this problem but its a core mechanic problem,which cannot be solve without taking the fun out of running.
In Medal of Honor(2010) you had several multiplayer modes develop by dice,these modes used FB1.5 technology(Same as BC2),the thing about its design is that it solves all the problems that exists on COD multiplayer,For what I have seen from BF3 gameplay videos, infantry gameplay will be awfully similar to the one on MoH,the thing about MoH mutiplayer its that it has a minimal amount of quick-scooping,its classes are quite balanced and bullets have their own physics,making impossible to aimboters to use the sniper power as shotguns,apart from that,the level design and game modes are far more entertaining and better planned(specially tactical mission,which is goldrush from BC),so infantry gameplay has a lot of potential(specially on 64 maps like operation metro shown in E3 gameplay,which fortunately is infantry only).
Which brings me to the potential gamebreaker that might potentially spoil the BF experience,the jets,the problem with jets in BF games is that unlike the perks on MW series, the jets don't run out of time,can be repair and re-arm and an skilled pilot can easily achieve 80 kills in a round,the strongest point of BF is the usage of vehicles and the destructible scenery(which in itself also helps the game to be more fluid,avoid camping and makes the players plan better strategies for attack and so on)but the usage of jets is a problem,jets can only be shot down by AA or other jets,an skilful pilot can dodge AA and destroy other aircraft quite easily(specially with the J-10 on BF2),helicopters can be shoot down with conventional RPG but an RPG cannot hit a jet(well it can but it will be a heck of a shoot),but the problem with destructible scenery its the lack of cover from air attacks,I'm not sure how DICE will tackle this issue but I'm pretty sure it will be a horrendous problem with maps that contain aircraft on them.
As I said,I don't think that BF3 will be better than MW3,the problem is that MW3 will be an outdated game compared with BF3,I will buy both games(MW3 mostly for the single player,after all singleplayer has some of the best level design currently on the market) and BF3 once I know If I have to say on my currently location,or I have to move into somewhere else(other country),I've to build a gaming rig for it and I'm still getting my head around that problem.
But,I have to say that BF games are more time demanding,and more stressing when you are not in a good team,COD doesn't have too much effect on this because is more oriented to individual play,while BF is based on teamwork,so If you want something to play in daily nights,play MW3,if you have all weekend free play BF,apart from that,is all up to the person who plays it, I'm personally tired of COD,multipayer in black ops is not as good as MP in MW2,and playing the same maps(8 I think)over and over again gets really tiring(the level design its incredible but after 2 or 3 hours of play for two months they get too repetitive).
With that said,I could not care less about COD elite or BF's thing,I studied them a bit and Elite is just Bungie's Halo 3 web thing,the same can be said about BF's thing,statistics and gameplay data are not as important and noone checks that anyway,what is important is overpowered SP weapons,but as claimers said,new weapons are just mere aesthetic objects with different attributes,but designed to still be balanced during gameplay so for me both things(Elite and BF's thing)are meh.
(I wrote a lot,pretty much bad written but I'm pretty sure that this covers all I wanted to say about both games,in conclusion,I will stick with BF3 infantry maps)