Agree with Adam above....new member as well and was directed here by Atomic (Ross) many months before i actually joined. I have enjoyed using both, and agree that Facebook fills the quick hit questions/topics a little better. Of course this may be to the fact i have used Facebook for years and it is second nature to just randomly check it during the day, and pretty much leave it parked on the INDMAS group.
I personally don't have any issue if the decision is made to lock down the Facebook group to either paid members or making a no "buy/sell" rule on it. Just know that they have other options to use for this, and doesn't mean it will drive them to use this site. If they are already paid members i am sure they will use it, but if not they will just join one of the other local Facebook groups like 'Central Indiana Saltwater Enthusiast' or 'Central Indiana Aquatic Resale'. I see the for same items for sale in the different groups all the time, many are from people on here. Which i think is fine, more places posted the more potential buyers. You will never get those who are looking for a selling spot to pay the $20 just to have another place listed, too many free options out there.
In the end you will have those willing to pay the $20 to be a part of something more and support a good cause, get to know others in the hobby, etc. Others will get that feeling just being a part of a Facebook group.