First the facts:
No AA filter or a reduced AA (AA cancellation) is going to offer more resolution. No question about it.
However, there WILL be artifacts and moire in certain images and more resolution may decrease it some, it is never completely eliminated.
These are the facts -
Now for my opinions.
For a lot of photography, you won't have issues with artifacts and moire. So go with the R and don't worry about it. On the other hand, the extra sharpness can only be realized and taken advantage of on huge prints or with a lot of cropping - thus it might just be a wash. Who is your audience? If it is anyone other than a photo critic, you're good. Moire? Artifacts? Sure, they aren't that common, but even so - does the average person notice? No.
On the other hand,
The absence of AA filters and the move away from them is a somewhat disappointing indicator of what is going on in the world of digital photography. In other words, the lack of desire for this feature indicates a decreasing amount of knowledge by photographers or at least those who buy photographic equipment, and it also indicates a decline in the standards of photo excellence.
It is far preferable to lose a little bit of resolution, than it is to have moire or artifacts in your image. At least to a discerning eye or a critic. Or to those who know what they're doing. Moire, to those who can recognize quality, sticks out very much and is a visual annoyance. It is also the mark of an amateur.
In the internet world though, having an AA filter is like leprosy. Nikon has done away with it on many of their cameras. Canon still holds on, and for good reason. Nikon is pandering to the consumer demand - even though consumers don't always know what is best for them. This is a failure on the part of Canon to educate the market. Unfortunate for Canon, because the burden falls on them to convince people why they need something that on the surface appears to hinder IQ, not enhance it. While Nikon just removes the filter - and the internet is all about reviews with pixel-peeping and the ONLY lesson learned is all out resolution is better. Canon wins on practicality, Nikon wins in marketing.
And there is a big difference between high resolution and high image quality. Many confuse the two.
Even at the start, Nikon at least offered their platform owners an option. They did away with that. Canon fortunately is giving their users the option. Hopefully, they don't follow suit and do away with the AA filter entirely.
Average people who know nothing about photography aside,
For the vast majority of photography, an AA filter is a great thing to have on a camera sensor. Regardless of resolution. But what about without? The 5DSR has its place. No AA filter is perfectly fine in CONTROLLED ENVIRONMENTS. Such as a studio. Where you can avoid textures, fabrics or whatever repeating pattern that might generate moire. That way, you can extract the maximum possible resolution from the image for gigantic prints. Not only that, but within the studio - you must have complete creative control too. If you don't have complete creative control - you are still stuck photographing things that may cause moire.
Outside the studio, the AA filter is a big help. You can't control what people wear, or patterns on roofs or buildings, or walls, or carpets or whatever it may be.
But what are the downsides? AA filter does indeed intentionally blur the image. Does it matter? NO! Not for the vast majority of photography. Again, if we're discussing the utmost in super cropped, pixel peeping madness you won't get the same total resolution as the non-AA filter sensor. But for everything else, it is completely unnoticeable.
To put it simply, you WILL NOT see the resolution penalty on an AA filter, but you CAN see the moire on the sensor without AA.
It is a trade-off. The geek in me wants all out resolution to pixel peep and admire the detail. However, the realist in me knows this doesn't mean squat anywhere else except for within Lightroom, and I'd rather not get stuck with some heinous moire that will ruin a nice photo even at normal viewing sizes.
I prefer AA.
