Hi Andy and welcome to the forums. Im not an expert on either but I'll pass on what I do know.
Rats and degus alike are both alot happier when kept in same sex groups, especially degus who are supposed to have a longer life span when kept in a group than on their own.
If you want interaction a rat would probably suit you better as degu are very inquistive and will be off like a shot to explore anything in their sight, this might be you to sometimes but not always!
Another thing with degu is where you'e going to home them, normal plastic based cages are a no-no as they will chew straight through. An aquarium or full wire cage are the best options.
Both rats and degus are highly intelligent so need lots of things in their home for stimulation, multi-levels, tubes, things to chew on and play with.
Also degus cannot tolerate any suger so you have to be particularly careful with their diet and the treats you give.
I can't think of anything else at the moment but hope that helps you a bit, i'm sure you'll find someone on here who can give you more info.
