Definitely the Neo Vent!
Not owning a B3 or a Leslie 122 or a car big enough to cart them around in, or the strength to lift them, I have another solution which suits me fine. I have programmed many B3 voices into a Roland A-90, added a Roland EV-5 Expression pedal, and the Neo Vent, and the result is great. The Neo is slightly bigger than two effects pedals side by side and weighs one kg but is more versatile than a Leslie as the two speeds can be varied and the phase effect shifted. So portable and light weight!
Not for the purist perhaps as there are no drawbars, but arranging the voices in sequence on the A-90 (or an RD-700 or whatever) means you change voices with the up/down button. And you split the keyboard so if using a walking bass with the left hand it is not affected by the expression pedal.
As I also use the EV-5 for organ sounds with other keyboards with reverse polarity to the Roland (notably a Technics KN2000 which has its own Leslie effect which can be cancelled and replaced by the Neo) I added a polarity switch to the EV-5. Now it can be used by keyboards of either polarity.
The Neo is true to the Leslie sound and eliminates the humping around of large speakers.
A great solution I find.