pic: If you had made it out of steel . . . . .

[Frank(Aflak)]

if your wheels are good and the bearnings in them are efficient, no more power loss than your standard tank drive going straight.

What you have to remember, though, is that your 'real' speed will be higher than the speed a normal wheel would go for the same RPM, so you want to wheel spinning a little slower than you need . .

basically, the drive base is a gearing up, less power, more speed for the same shaft RPM.

otherwise, if your omni wheels are good, the only disadvantage is working with such a weird drive base and explaining it a million times to the curious.