The European-style bidet does require extra real estate in your bathroom. The Japanese-style washlet does not; it's built into the toilet (or replaces the regular lid).

Honestly, I have no idea why Europeans still use their old-fashioned bidets now that washlets have been around for several decades. Why would you want to use two different devices just to do a #2 when you can just sit on one and get it all done at once?