My team has never used an omni drive train, but I do know a little bit about them. Please correct me, anyone, if I am incorrect in any of these statements, and I hope this can answer some questions.
Holonomic Drive: More prevalent in FTC, it uses 4 omni wheels with 2 sets of 2 perpendicular to one another. In theory, this drive should be able to drive in any direction, but my understanding of why this isn't used in FRC is because of a terrible lack of traction and difficult programming.
Slide Drive: Also known as H-Drive, it provides around the same maneuverability as a mecanum drive, at the expense of the weight of an extra drive motor (for strafing).
Omni Drive: I don't really have a name for this, but it is what
33 and
team JVN (VEX BuildBlitz) used this year. It was a 4WD, with omnis instead of traction wheels. I do not really have any info on this one, except I have been told that it allows for easy drifting and better handling.
Butterfly Drive: This drive is derived from octocanum, which was derived from nonadrive. The only difference between octocanum and butterfly is that omni wheels (butterfly) are used instead of mecanum wheels (octocanum). Butterfly articulates between traction and omniwheels, usually with the traction wheels geared low and the omni geared high. An example from this year is
3847.
Nonadrive: I may not be totally correct on this one, but it was first used in 2010 by teams
148 and 217. The difference between this and butterfly is that a slide wheel for strafing is deployed during the omni phase to allow for strafing.
In the end, to your question for driving, it all depends on how much time the driver has to practice, and how good the driver is.