Upload & Sell: On
I shoot motorsport for a living (not getting rich) and I think the answer to your question is first that you can take good bike shots both pan and head-on both with and without a monopod. Second, I don't know anyone who uses a head on a monopod...for anything.
I use lenses from a fisheye to the 600 f4 for on track shots. I never use a monopod with anything 300 or under. For anything over 300....sometimes I do and sometimes I don't. I don't remember ever intentionally using VR when panning but I know people who do. The secret to getting good shots both with and without is that there is no secret. It is all about technique and what you are trying to get. In-other-words, with or without you can develop the skills to take good pictures. There is no "correct" way to do this.
I basically agree with Carl Auer, above, about taking a monopod. Take pictures both ways and just try to get comfortable. I guess I tend to use the pod more for head-ons with the longer glass and less for side action pans. With head-ons you need less swing....why wear out your arms?
Here are a few of my Moto GP shots from last year's action at Indianapolis (links from the IMS website). The first one was shot from the top of a building panning down at the track with a monopod and no head (with a 400 f2.8 I think).
This second shot was shot hand held with a 500 f4 or a 600 f4.
This one was with a shorter lens, 200 maybe, hand held.
None of us is perfect and we all hopefully learn every time we go out. Go with a pod and shoot both ways. See what feels better. Sometimes just getting a few shots to come out is worth it.