CNC Mill or Router?

[Lireal]

This year, my team found itself with extra money in the budget, and we would like expand our program by getting either a a cnc mill or cnc router. We most likely will not be able to get both of them within the foreseeable future, since this is happening under some strange circumstance.

Our budget for this would be about $4000-5000.

From your experience, is a cnc mill or cnc router more useful to have by itself? What size of each would be sufficient for an average team?