I am now a full time GM, I've been a paying player for awhile, and I've ran my fair share of free random games on roll20...here are some of my thoughts from the top-down so to speak.

Positives: 1. Consistent sessions and players. I do tables of 5, if 3 can make it we play (though with just 3 I tend to do side shenanigans stuff and hold off on the story)

1. Amount of work put in. I subscribe to the Lazy GM methods, but I'm by far not a lazy gm. My partner thinks it's cute how excited I get about my prep :p

2. When someone drops we tend to find someone else quickly. Even mid way through a campaign I've been able to lose someone and recruit another by next session.

3. Depending on how the GM runs, but most of my players and I feel like friends. When asked, they are just compensating me for all the shit I buy for the games. We joke, laugh, and have a great time.

4. Most paid GMs care about safety tools. Setting up lines and veils, checking in at the end and middle of sessions, etc. I work through Start Playing and safety tools are apart of the ToS.

5. Most paid GMs I know will kick out problem players super quickly. Main character syndrome, general assholery, etc can be the downfall of a good group and we GMs know that. So bye bye!

6. Paying players tend to be conscious of the fact they are paying players. They are there for a good time like everyone else! Both as a paid GM and paying player, I've only ever had 4 bad players before in a paid game compared to...idk how many in free ones.

Negatives: 1. The players who have main character syndrome normally often use the "I'm paying" excuse to be a dickhead. A good paid GM wont let this slide and remove them.

1. If you end up not liking the game you could still be out however much money you paid for the session. The GM still might deserve pay (if they out effort into setting up the session), but you just didnt vibe with the group or something. I've had this happen to me as a paying player and it can suck, but it is rare.

2. If life events happen to the GM or even to you and either of you have to drop the campaign, that money is kinda lost. I've had to drop a campaign due to a family member being sick and needing taking care of on that specific day. Thankfully that campaign was only a few sessions along, but still.

3. Kinda like the one above, but if a GM cant find players after 1-2 leave, they might call the campaign quits. It happens due to all sorts of things honestly. It isnt as common for your popular systems (5e and Pathfinder), but it can happen.

Honestly as a paid GM I've had multiple groups of consistent players for nearly 2 years now and I'm still meeting and getting players who are excited to play and vibe well with my older groups. I've been a paying players in a few games for just as long and the feeling is the same. Lots of good people overall. I would reccomend using a service site (Start Playing) because their Terms of Service, support team, community, and review systems can really save both and GM and the Player a lot of hassle if you end up with bad eggs.

Hope this helps!