To be honest, the vast majority of those things will work in both just fine. I certainly wouldn't say Poser is better for compatibility. Daz has the genesis stuff exclusively but the vast majority of things you find on the Daz website will work on Poser (as on renderosity). Just be careful to check, but honestly I've never had a problem with it and I buy a lot from here and from Daz.

What I'm really trying to say is that it's not an issue that should decide your choice of program. You won't want for content with either choice.

They're both fine programs. I strongly suggest you give yourself some time with both of them and make your choice based on what you find you can get results with.