There's a small variety right now.
The two sims with the most traffic (47k-54k) are Laura Outpost and Ar. Although I'm not sure how accurate this is because I've seen multiple AFKers on Ar (usually the sim mods and owners) at any given time. I've also met a player there who keeps more than at least one avatar on the sim and RPs with both at the same time. Ar is new (opened 9/7) and are still finding their way in terms of administration and stories that generate sim-wide RP. The sim layout in Ar is nice, and the build looks good.
A lot of old school players in Laura. I prefer the administration/RP there too. They have some strong inter-sim relationships that keep things dynamic.
Quality of RP in Svago was good when I visited. The sim owners were on a small hiatus and traffic tanked to under 2k; they're back and are building it up again. They're very welcoming. There is a tavern, inn, and merchant shops in the lower city. Upper city is gated off... so this means that for visitors you'd better come in with a compelling story or your RP will be sitting and drinking and socializing with some small talk.
There is also Hochburg (~30k), they have their vision outlined in a notecard:
Hochburg only has one group tag. It is the same for everyone. It is not often one travels somewhere and is able to tell their name and position by the tag above their head. However, I have not read “Name Tags of Gor” yet so I could be wrong. If one wishes to find out who someone is all they have to do is make for introduction in character. It’s not a difficult thing to do.
Hochburg does not incorporate notecards into their role play system. If an individual wants to role-play getting their slave an exam or having slave papers or free companionship papers drawn up by a scribe, they are certainly welcome to do so. Is it a requirement for these things to be done in order to role-play in this SIM? Of course it isn’t.
Paragraph posting RP in all 3 of the above.
"The difference between reality and fiction? Fiction has to make sense." Tom Clancy