[i]I agree with all that has been said so far ^^
But I will say this before I do my list; I have never done advanced because I don't feel confident in my writing skills- though I like the development those roleplays go into. Anywho, here is MY little pro/con list for ya from experience:

Free Pros:
- Fast paced, keeps the roleplay moving and going within days
- Actual start up time is faster from interest check -> ooc -> ic.
- If you're active online one night, you get to roleplay ALOT
- You don't have to worry too much.

Free Cons:
- Sometimes TOO fast paced, you get left behind- sometimes forgotten.
- If you're NOT active online one night, you get to READ the roleplay ALOT
- You're not worrying and neither is someone else- so they don't care, which sucks.
- One liners... :c
- txt spek &&& comon spelling misteaks!
- Roleplay disbands/dies quickly

Casual Pros:
- Lots of people here to role play with
- Lots of various skills here to role play with
- Matches best with my schedule of 1-2+ posts a day
- Let's me get more creative and in depth with my characters
- Usually some rules placed to help avoid 1 liners, txt speak, god modding, power playing, etc.

Casual Cons:
- Lots of various skills here to roleplay with
- My in depth characters usually don't get used cause at least all the roleplays I have joined die eventually. (days..weeks, months)

In the end, Casual is my favorite section but I do go in Free if I want to just have ALOT of mindless role plays to pass my time while i'm here. I really recommend coming to casual and roleplaying there sometime. It might be scary at first- I know when I first came to the guild I did free and strictly free (Even though I'd write more than 1,2 paragraphs every time I posted) cause I was way too scared to leave those boundaries.. but its not that scary :D and I bet you'll love it.

If anything, come join a role play of mine in the future- cause I'm a pretty friendly and cool GM! 
[/i]