From personal experience, I would vote neither. D&D to me is not a ruleset, or a setting, it is a set of common shared themes and experiences centered around adventure.
I started playing in late '81, we mixed elements of the Moldvay Basic set and the AD&D PHB because that was all we had. They were different rulesets, and there was no real setting, but we had elves and dwarves and fighters, and wizards going on adventures and it was D&D.
There times we would play D&D in study hall or at recess, we didn't have books, or dice or character sheets, just one guy DMing and a coin to flip anf the rest of us playing Falstaff the Fighter and Grimstar the MAgic-USer, etc. and winging it all, flip a coin, heads you hit, tails you miss, etc. And to us, it was D&D by god.
I moved just before high school, found a new group o play with and played a lot. Full on AD&D now, Greyhawk, Dagonlance, didn;t matter, it was all D&D, adventuerers adventuring. Magic, dragons, orcs, thieves, etc. Then our DM got the Rolemaster stuff, and we started using it while going through Dragonlance, Greyhawk whatever, the rules were different, but we were playing D&D baby, at least in our minds no matter who said otherwise.
2E rolls around, while I am in college, I find a new group post college, they play in the Realms, we add all the 2E stuff, kits, etc, but it's still D&D to us. We had magic sers and clerics, fighters and thieves, bards and barbarians monsters, magiuc and mayhem, it wa about adventure and fun, not rules and setting.
SO now we have d20 and it is a different ruleset and there are different settings, but it' still D&D to me, as is Castles & Crusades, True 20, etc. because rules and setting is all secondary to the experience of playing, of having characters going on fantasy adventures with magic and combat and wizards and well and dungeons and dragons you know.
And so 4E is on the horizon, and it will be different. Yet not really. Because in the end I will gather with friends and roll some dice and go on adventures or run them through some adventures, And there will be wizards and warriors, tunnels and trolls, runes and quests, casles and crusades and yes, dungeons and dragons. And if we want, we can choose the rules and choose the setitng that works best for us, or we can gather up in study hall with a coin to flip and our imaginations, but we are all stillplaying Dungeons & Dragons.
The brand identity, it's our connection with that set of experiences. The rest is all jsut the details of how it plays out, it is not the experience itself.
-M