The one I have (heh, actually I have quite a few of them now) is the Sanyo MBC-55x series. It's notable for being the slowest MS-DOS compatible machine (3.58MHz). I do notice a speed difference, even on this machine's rather gimped memory bus (half of the RAM bandwidth is devoted to the proprietary video hardware). In theory, the speed difference should be more noticeable with a machine with a proper fully devoted CPU memory subsystem, because the V20 can chew through instructions with less clocks, making it more able to saturate the memory bus.

The speed differences actually cause it some minor compatibility problems. If a CGA video card is installed, Sanyo's video BIOS can't keep snow off the screen during BIOS video operations (pretty minor), but also Sanyo's disk format and disk copy utilities don't work at all (I wrote a couple very limited replacements). This machine has no DMA mechanism at all, so floppy data needs to be moved by the CPU as it arrives at the chip, and this is a very timing sensitive operation.

When I wrote my BIOS for it (I wanted to run FreeDOS and also I added an AES floppy encryption mode, for "reasons"), the only part I really had to cheat at and look at how Sanyo did it was the floppy data pump code. It taught me how critical using the memory bus effectively was on this machine - going by the typical "8088 instruction cycle count" lists on the internet does not get you to the right kind of code for that part.

I was pretty amused to work around one of the most glaring Sanyo BIOS implementation bugs - the real time clock (emulated via timer chip) would lose time when accessing the floppy, because interrupts were disabled. They had another channel chained from the one they used on the timer chip - all that was necessary was monitoring the second channel for overflows from the first one.