Well, see, that's a really personal thing- I am SO picky about shoes, especially sports shoes. I don't see how people can stand Keds they're such lousy shoes. Culturally they're the same as foot binding- "Oh, I'm helpless!".
I find better equipment gives better performance, and I expect to put out the same on a spin bike as outside. Spin was started as a training thing by cyclists, and was ripped off and made into a gym gimmick. The name is spin because that was the point- work on the finer points of technique and perfect your spin. You can do aerobic conditioning any old way and it transfers. A spin bike gives you a venue to pedal squares all off season.
Frankly, I don't really get the multi shoe thing. I use ATAC, so mt shoes are out. Therefore, you take your road shoes and use the LOOK side. How many pairs of cleats do you want to set up?

Lizzy