Are you talking about working as an ER doc or an ECC residency program?
In a perfect world with no bills and no school loans, would rather do an internship, but I am not sure finances will allow it. That's why I wondered about working as an ER doc right out of school.
I think you could do it without an internship, but you should seek an emergency practice where you would be with 2+ more experienced, skilled and passionate veterinarian(s) (ideal=board certified) willing/able to mentor you. You don't want to be by yourself with 1 tech at 2 AM with your first GDV or a spleen that needs to come out.
If it's a progressive high-quality practice with some key tools useful to ER (good diagnostic equipment), skilled/trained/experienced tech(s), and again, early mentorship, it could be a great opportunity.
Just don't get stuck in that, Hey you've been out 3 months, now you're good to handle overnights [alone]!
IMO, it's the caseload/mentoring and experiences you'll get. I don't necessarily think that all internships will equate to 3 or 5 years experience. I've seen some interns that did 1 year at XYZ place, and they are GREAT and I've seen others that, I'd rather have the 3-5 year-experienced-grad-no-internship. It really depends on where you are, doing what, and with who, and your own level of committment to learning and improving.