Instruction in the US could be equally good compared to f.e. the UK but it's also a fact that the FAA will allow schools and instructors who won't do a good job. I'm sure that Bell school provides very good quality of instruction but then it's starting to cost.
You shouldn't lump everyone together but there is an attitude of "I just want to build my hours" among many US CFI's. Being able to work as an instructor in the US is of course valuable but do keep in mind that you are not welcome in the US anymore when you want to continue your career. A 1000 hours of instruction given is great but not necessarily your ticket (after you have converted to JAR of course) to commercial work in Europe.