First.. nothing beats a drumscan. Any decent drumscan is still lightyears ahead of even the best flatbedscan.
Something you might want to take into consideration is the focusable lens in the 10000XL. Although the maximum resolution and the dynamic range of the V750 is superior, the 10000XL provides very sharp scans thanks to the focusable lens. I personally like my filmgrain sharp, although it's of less significance with 4x5 film. Probably a matter of personal taste but then again, if you shoot 4x5 you're most likely a sucker for sharp photographs in general.
Either way you won't get disappointed by any of the two Epson scanners. I have scanned a number of exhibition projects with both scanners and even the rather critical photographers didn't expect to get this kind of quality in their prints from the Epsons. The quality between the two is about the same with the (minor) differences mentioned above.
The 10k is built for commercial use and the sheer size of the machine wouldn't make it the ideal choice for home use. Unless you have lots of open desk space. Hope this helps with your decision.
Best, JAN.