I have heard that there are Vets who dont like thier clients there where thier pet is euthanized, as they get very emotinal and sometimes go into hysterics.
A good Vet will understand though, and will realize that for your own peace of mind that you will want to be there for your pet, the way that your pet has been there for you all those yeras.
I have been told that the emergency vets charge more for things as thier business is a lot more sporadic that the regular vets, and it costs more to have staff there all night.