FlyBus is the one I fly for - I like it’s generic fictional anywhere-you-want airline approach.
It’s got a very well laid out dashboard website and once you get everything set up, you can have your flights planned out, simbrief’d and vatsim’d (or plugged into any other ATC of your choice) with only a few clicks.
Also, there isn’t too much in the way of minimum requirements nor availability expectations. It’s a very relaxed environment that brings you the best of the VA experience without any of the commonly associated drawbacks.
Plus, I think the liveries look pretty snazzy as well.
Very good ACARS software too, all handily available in their website (no need to hunt around the nets to download stuff) - It is also sim-agnostic, so if you wanna use X-Plane, it works just exactly alike, same software and all. Just setup the plugins on either sim and it sorts itself out.
10/10