I have experimented with all three leslies on the Helix. Better or worse results depending on which one. The Fender vibratone clone is the best of the lot for me, then 145 then 122. I have found that depending on the IR I'm using (I use nearly all third party IRs from The Amp Factory or OH) and the amp sim, sometimes it's best to have the rotary on it's own with cab IR disabled but sometimes it sounds good to me with the cab IR on and the rotary on (either directly after IR, on path A or dropped down on eto path B and "mixed" in with the cab IR.
I also have exp. 1 set to blend the mix of the rotary into the main guitar signal so, on the presents with cab IR on all the time, I can bring the Leslie/Vibe in as much as I want. That, for me, was a very cool find in the controllers. I do make sure to cut the max speed down some from the full speed the sim is capable of running. At max for me, I like it in the 5-6 range and low speed in the 1-1.5 range.
edit: I also have some (light) reverb in the background too, simulating a room, usually. I like the depth this adds to the sound.