Unless you have a specific workflow-related reason to *NOT* shoot full RAW, there's no reason to shoot anything else.
If you're on assignment for somebody and said somebody has a specific setting, you obviously use that, no matter how silly it might seem to you. I've heard that Sports Illustrated only wants JPEGs, but I wouldn't even bet a cup of coffee that that's the case.
If your shots are going straight to the Web and nowhere else without any editing other than culling, you should shoot sRGB JPEG at your camera's lowest resolution (which will still be overkill). You should also use whatever picture style, sharpening, white balance, etc., settings that produce the results you want, and you should do whatever you need to to the exposure so that it looks good on the back of the camera.
Both cameras have ridiculously deep buffers even with full-resolution RAW...but, if you do happen to be in a situation where you need even more, shooting M-RAW or JPEG will practically let you fill up the card before the buffer fills up.
But for 95% of photographic situations where it makes sense to use one of these cameras in the first place, you should be shooting full RAW. Storage and processing power are cheap. Having to throw away that rare extra-special shot because you didn't nail the exposure or you can't enlarge it enough or whatever will cost far more than you might ever save by not spending another $200 on CF cards or hard disks.