Anyone who prefers the MP in MW2 over BO was probably a griefer, a booster, or rolled in parties and only enjoy MP games that are piss easy
While I prefer the weapons and maps in MW2, the balance was an absolute joke with countless moronic decisions by IW. Obnoxious killstreaks + stacking (predator -> harrier -> pavelow/ac130/cgunner all day everyday) made objective modes outside s&d prolonged TDM's, only a handful of weapons are ever really used, gamebreaking perks, snipers with strong autoaim making quickscoping a legitimate strategy, akimbo 1887's, and worst of all significant glitches, hacks, etc. on a weekly basis. BO was such a vast improvement over MW2 in MP that's it's a shame it seems like some things will be reverted back to the way they were seeing as how killstreak stacking is still in.
And to anyone who buys IW saying things will be balanced, remember what was said before MW2's release (such as the "rare" nuke).