The current, more expensive 2013 iMac 21,5" model does have a Nvidia GT 705M w/ 1 GB GDDR5 VRAM, but no upgrade option. Don't know whether that's much of a jump, performance-wise. I tend to upgrade my iMacs in a 3-year cycle, where performance differences are much more noticeable.

Mind you, I'm seeing minor delays in texture replacements, too. In crowded places, armor textures on PCs and NPCs get replaced from a low-res to a higher-res version only at very close distances. The switch is near-instant, but since it's so close in the view-port, it's very distinctive. And this is on the current 27" top model with a PCI-SSD and the 4GB VRAM Nvidia GTX 780M, where memory throughput and size shouldn't be an issue.

My current pet theory is that with the ongoing memory management related crashes (see this thread for further discussion, and you can post your Crash Reports here), they've turned LOD distance way down to alleviate the 32-bit, 4 GB virtual address space limitations. After all, their engine should be able to display several hundreds of players in an AvA situation simultaneously, so it needs to be stingy with memory.

So before you go throwing money at Apple, I'd do the following:

• wait for ZOS to release a 64-bit game client. It should lift almost all limitations of the current 32-bit client app. A 64-bit client has not yet been announced officially.
• if your Mac still runs on rotating magnetic disks, try installing the game to an external Thunderbolt-SSD. A fast one, preferably, though you'd have to find a sweet spot, price-wise.

Edit: typo

I agree with @KhajitFurTrader that it really is not a big performance upgrade between those GPU. it is one of the limiting factors in the 21.5 inch iMac currently that they don't offer an upgrade option.

The current, more expensive 2013 iMac 21,5" model does have a Nvidia GT 705M w/ 1 GB GDDR5 VRAM, but no upgrade option. Don't know whether that's much of a jump, performance-wise. I tend to upgrade my iMacs in a 3-year cycle, where performance differences are much more noticeable.

I do exactly the same now for 10 years as it gives the best balance of actual upgrade v cost. I always go for the best GPU option as they are not replaceable.

Mind you, I'm seeing minor delays in texture replacements, too. In crowded places, armor textures on PCs and NPCs get replaced from a low-res to a higher-res version only at very close distances. The switch is near-instant, but since it's so close in the view-port, it's very distinctive. And this is on the current 27" top model with a PCI-SSD and the 4GB VRAM Nvidia GTX 780M, where memory throughput and size shouldn't be an issue.

My current pet theory is that with the ongoing memory management related crashes (see this thread for further discussion, and you can post your Crash Reports here), they've turned LOD distance way down to alleviate the 32-bit, 4 GB virtual address space limitations. After all, their engine should be able to display several hundreds of players in an AvA situation simultaneously, so it needs to be stingy with memory.

It's as I confirmed in the other thread. The LOD isn't being reduced across the board but that when it hits a predetermined level of RM it scales it down. This is WiP (being adjusted in response to launch data/feedback) It's the balance between the demand in big battles (loads of players) and just general questing.

Nvidia GT 705M > 750M

Great info as ever.