Project vs. Product work
There is no work quite as soul destroying as trying to replicate an error. That's why I'd choose project work over product work any time. With product work, when a client in Alaska gets an obscure error - you have to try and simulate it. This can take hours and hours. And the end result isn't nice code and a functioning program, the end result is a BUG. Only then can you get back to creative work by fixing the bug.
When you are doing project work and something goes wrong, you've got access to the production server. It's muuuch easier to solve the problem.
So, if I could choose between product or project... bring on the project.