I watched for a few minutes but I'm still not 100% sure what is being compared. I'm assuming graphics. If that's the case, then I'm indifferent. I like both. They're both very samey in the first place. The environment is just drastically different. So it's a bit hard to compare.
Now, if we use singleplayer and multiplayer... Without sounding like an extremely long-winded sh*tface; ACB/R multiplayer, to me, was simply intolerable. I hated it with every fiber of my being.
Whereas I actually really look forward to getting a few matches in on AC3. It's extremely enjoyable. When I die, I died on purpose. When I kill, I earned it. I expected to go in just for the achievements and instead came out with what will be, probably, my staple game for the rest of the year (at least.) --- Currently Playing: AC3, FFXI(Que.), FFXIII-2, GGXXAC+, LoZ: Skyward Sword, MW3, Valkyria Chronicles
I never used Medicine, besides if I occasionally fell off a building, so that never affected me, you had to actually do more than just hold block the whole fight then either disarm or counter while in slow motion like this game. Disarming, and countering with the hidden blade actually required timing or you'd get hit. You could also dodge.
I've literally never gone below 80% health in this game, it's all the same. Counter regular guards, and those dudes that do the roll, break officers and heavy's defense (or disarm them), disarm jagers. If it at least had some sort of penalty for just blocking the whole fight then pressing one button while in slow mo it would be somewhat difficult.
~realistic.... notice the video title "...gameplay comparison ". Im showing off the differences in gameplay between the 2 games. If you look, you can see that Ac3 has one button for freerunning and is smoother. And with the different settings, the way/things you climb is different.
Also, the combat is altered quite a bit. Ac3 feels harder due to no health upgrades, or potions, and sometimes more than one enemy attacks/shoots you. But an argument can be made for 2 as well.
Oh, and forgive the bad ac2 gameplay, i'm quite rusty and spoiled from 3's one button for freerunning.
p.s. its AC2 vs AC3, because I don't have 1 anymore, and 2 makes a more interesting comparison (i think)