There are a lot of advantages to rendering your characters in Maya. You get the benefit of Maya's far superior lighting system and rendering engines, particle effects, dynamics or any other feature of Maya you would care to use. Although, you may be happier just setting up a Poser based mesh for animation within Maya natively without the need for Poser at all. I don't know the people at Reiss personally but have communicated with them through email and they are super nice folks.