The US site lists the S5Z as having MPEG4, but neither the specs in dpreview or the British Pentax site list it for the S5n.
The older format 640 X 480 movies at 30fps are every bit as good as MPEG4. The movies just take more space on the card.
I found a British review of the S5n. It said it is nearly identical to the S5i except for the larger LCD, no viewfinder and better movie mode. They also didn’t list MPEG4. If times are the same as the S5i it isn’t nearly as quick as the Z750:
http://www.imaging-resource.com/PRODS/S5I/S5IDATA.HTM
The Casio S500 is already available overseas and will be available everywhere shortly. You might want to wait for that if you want a tiny camera. You get MPEG4 and don’t have to give up the great past movie mode.