Aids can be good or bad depending on the drivers in the lobby and the experience level you’re seeking in the lobby. For example, the driving line helps the newer and less familiar at a given track. This can help the experienced as well. That new guy that doesn't know the track that well will know there is a braking zone ahead and just might stop in time to keep from punting you into the dirt. On the other hand, not having the driving line on may discourage new guys from joining in as they don't want to be left behind or endanger other drivers.
Traction Control is always a good thing to allow. Those that use it are most likely going to be slower and give those without it an advantage. The other aids (with the exception of SRF) are a mixed bag and normally do not make or break one’s ability to turn quick laps. I find that they slow me down (except ABS, where I prefer a setting of 1).
SRF is a good aid to have when you first start driving online. Once you become experienced and learn car control, SRF then becomes an edge. It makes sense if you want to race against more experienced driver to not allow it. This will ensure that the inexperienced will be left spinning of the track at the first sharp corner leaving the experienced drivers to compete with each other.
Of course some like the arcade experience and have all aids on, drafting at strong, boost all the way up. This creates a room where the inexperienced have a decent shot of keeping up with the experienced and can make for some fun pack racing.
So it depends on what kind of online experience you are looking for. Just fun...leave aids on. Serious racing...start turning them off.
I prefer lobbies where the top three (SRF, AS, and ASM) are prohibited, and the bottom three (DL, TC, and ABS) are available. This seems to attract a decent mix of skill levels and makes for a fun online experience.