You'd be surprised. I imagine consoles have texture size limits of 256x256 (maybe 512x512), while PC's can theoretically handle anything, where 2048x2048 is become more and more common for "HD"/Ultra modes. I'm not sure of the exact hardware in PS3 or 360, but i don't imagine they've got the power behind them to handle realistic large scale particle emitters like the PC can, at least not directly via the graphics section of the chip.
I've not looked into ARMA 2 yet but i have heard they're releasing (or have released) a free multiplayer version soon/quite recently.
With that said, i do believe it'll look truly breathtaking on every format
I wonder if that includes bots
To be honest, 256 bots on BF2 (the maximum allowed) comes close to tearing down my 2600K, but it's well worth the drop in FPS in order to experience it. BF has been about massive skirmish since that title, so i expect BF3 to not disappoint at all. 64 Players was my favourite whenever i did go online (nothing short of awesome), and i guess playing AV in WoW reminded me of that style of gameplay (back when teamwork was so crucial).