Normal RAM can handle 1.35V typically and often goes up to 3200 MT/s (on AMD systems) or 3600 MT/s (on Intel systems). That's easily +20% to +35% more memory bandwidth. With lower latency and better overall specs to boot.
And if your 3d render has a pixel-error on frame 50, delete the .png file and rerender frame 50. No biggie.
As for me I'm just annoyed by the fact I have never seen a laptop that supports ECC (as for now it seems there actually are a couple of models e.g. ThinkPad P70). I personally don't really care about the RAM bandwidth, I'm still using DDR2 anyway, but I would love to use ECC.
If your 3D rendering has any pixel errors, replace the offending hardware. If your RAM is bad in one place, you need to replace it, ECC or not.
The RAM chip itself would do any computation if needed instead of the CPU, and if it needs to give interrupts to warn about error conditions, it could output it as an electric signal you can hook up to anything you want yourself (including to the CPU in some way, like via USB or something lower level, or otherwise a warning light or beep or so)