What makes a participant do these things??

[Dogmama]

I
But they also have these stationary bikes that have a little video screen mounted to the handlebars that shows other rides, a pace rider, and different scenes you choose. I've used that--it's cool! It has gears, the seat position is similar to my Hybrid, and I get a good work out. You can set the pace rider to go as slow/fast as you wish.

Is there an advantage to doing "spinning" over something like the virtual bike?

I think the answer is in your question. On the video screen bikes you said you said you get a good work out, the bike is similar to your hybrid and you like it. Perfect!