Canon R3

[Fast Glass]

I agree, except we already know what the specs are and what photographers have been getting in terms of battery life ect.

Yes there are a few things, but nothing in the real world that would make up for the advantages of the RF mount system and the R3 advantages. The one example I like to refer to is Froknowsphoto. The R3 with an RF 85mm f/1.2 (I have messed around with this lens myself) will continuously focus accurately on moving subjects with eye detect at full 30fps. This right here absolutely BLOWS away what the 1Dx III and 85mm f/1.2 II can do and I have used this combo quite a bit. It cannot reliable track anything like he did. It really is remarkable.

So will it blow out of the water the 1Dx III with fast focusing lenses like the blisteringly fast 70-200mm f/2.8 III (Again something I have used)? Not sure, but if the prior example is any indication of what it can do the 1Dx III is gonna have a run for it's money. If not destroyed.

It will most definitely make more sense it's positioning when the R1 comes out. But for now, unless the 1Dx III proves to have better AF. There is nothing it offers that would convince me it is a better body, it's just better in almost every way. And better in the practical ways that matters.

Only way I see it being viable is the used prices being significantly cheaper or if they price it below the R3. But at the moment with it being more money, it's a no brainer. Get the R3.

It's like comparing the 1Ds III to the 5D IV, the 5D IV squashes the 1Ds III where it really matters. But it is not built like a flagship or have certain things like dual slots, pro build, long battery life ect. It's not enough to make up it's short comings. Canon nor anyone would consider the 5D IV a flagship. But it is the better body and nobody would choose the 1Ds III over a 5D IV.

The 1Dx III might be built like a 1-Series, but it can't keep up with the latest and greatest.

I will say though, with all the bashing I do about the 1Dx III. It's still a ridiculously good camera in it's own right! I still loved that thing to death and it's amazing piece of kit. For the right price, I can see it being a popular choice for those who don't want to sink the cash into the RF system and is content with it's performance as a whole. I have been thinking about this option myself as I just can't justify the expense of the RF system right now. But IBIS seems really attractive to me.

Either that or just go for the R5, it's not exactly a slow body at 20fps.