I like the Baker F6R best because it's easiest to engage and disengage.
The F6R is all done within the trans, using the foot shifter. Baker does have a "safety" that you have to engage so you don't accidentally shift into reverse when you don't want to. The earlier F6R I had, had an electric solenoid safety and you pushed a button to activate it when shifting from 1st to reverse. The newest one I put on my 22 Road Glide has a cable operated safety with a little lever under the right hand grip. Both work the same way. From 1st gear, activate the safety and downshift into reverse. After you've backed up you simply upshift to 1st and you're good to go. Definitely easy and quick.
Unless it's changed, the Champion has a reverse shifter on the right side of the trans and you have to put the bike in neutral and then engage reverse. There's a little more of a timing issue to keep the gears from grinding when engaging reverse but once you get used to it, I don't think it's a real big issue. I have a friend that has had the Champion on her bike and it worked fine for her.
I also have the Yelvington reverse sprocket set up on on my Road King. It has to be put into neutral before and after using reverse. I don't care for this set up but it was the only one that would work with my RK DD7 set up. Not my favorite but it does go backwards when I need it.
When it's all said and done, all three units will get you going backward when you need to.
Just my opinions but I hope it helps.