I rode both systems, today I ride on Campy, and every so often get to ride a Shimano.. I miss the feel of the Shimano hoods, but I like the way Campy shifts.. so, for my next bike I will get whatever the bike comes with. The system will not be a factor in selecting a bike..
If I had 2 bikes, one for "racing" and one for long ride, I would equip the racing bike with Campy and the Centuries bike with Shimano.. But thats me.. I know some people feel a lot stronger about the groups..