Ahhhhhh ... we might as well get this annual conversation over with ...

I'll vote derailer -- ala Sheldon Brown -- since in most circumstances it is the better choice, IMO.

Essentially, I think that derailer systems are very robust to the point that the increased robustness of an IGH is not worthwhile in most circumstances. Derailer drivetrains are also more available, cheaper, lighter, and very easy to fix.

If you have a super small wheel -- roughly less than the 20" sizes -- then I would seriously consider an IGH. I would also consider an IGH for a multimode commuter.

D: 4
IGH: 2