Graphics - anti-aliasing and GPU load

I've taken a few months off Shogun and came back to it yesterday, after a patch or two probably. Since I had heard that AA was going to be enabled in one of them, I popped in to the graphics options and found the AA setting, it was off. Opened the drop down and it gives you a few options, can't recall the abbreviations, but basically there's a "new" AA mode that's comparable to old 4x AA that you can run with any shader model, and it supposedly puts less strain on the GPU, whereas the "old" AA 2x, 4x and 8x requires shader model 4 or 5?

I picked the new one and kept shader model 3.1 I think it was.

So the first thing I notice is that my XFX XXX Radeon HD 5870 did not spin it's fan up to the same speed it used to at the main menu. Some background is required here I guess. The XXX is factory clocked and the factory fan setting is pretty high, so I run software (MSI Afterburner I think) to set a temperature dependent fan speed setting curve, since the fan is VERY noisy above 50% speed. 50% speed or so is reached at about 60 degrees celsius with my mapping.

Before the patches, the fan would reach noisy speeds pretty quickly in Shogun, but yesterday, with the new anti-aliasing enabled, it never did. Not even after hours of playing. Early on I actually tabbed out to windows to check that the software was working properly and make sure my card wasn't overheating, this has happened twice, the fan not speeding up for some reason. But it was working fine, the GPU temp at 55 or so. When I was done playing I checked the temp log and it never went above 60, very stable for a very long time.

Has anyone else had similar experience post-patch after enabling AA or otherwise? Seems like a pretty significant improvement to me, the game didn't run slower or anything either, and while I have a hard time judging whether it actually looks any better, it sure doesn't look any worse, all my settings are still the same, ultra or high across the board.

Also, what is the "best" AA option? Is the new one preferable to 8x "old" AA? Does the load on the graphics card differ a lot?

Cheers
/Very happy with noise reduction