Originally Posted by somnambulant
If you don't have any preference over the races, I'd say go for Belgium. I think the Belgians like their bike racing more than the Dutch, but correct me if I'm wrong. Having good fans around you might be more fun. And hell, there's nothing stopping you from visiting Amsterdam anyway, right? It's not like Belgium and the Netherlands are far from each other. Just spend 2-3 days in each country and you're good to go.
For the bikes and racing Belgium is the better bet. For everything else the Netherlands rules. If you decide to stop in Amsterdam or Rotterdam let me know and I can hook you up with some of my friends there. Nothing like some locals to show you around and take you to the cool spots. The velodrome in Ghent is awesome and they always have old rental bikes for sale for cheap. There is also a track store around the corner from the Velo with all manner of track stuff. I found a bigger language gap in Belgium vs Netherlands also. Pretty much everyone speaks English in Holland.