I say keep the edge sharp if you want to throw the water out beyond the wall. If you want it to cascade down the front of the wall, add bullnose. The effect will also depend on the speed and volume of water.

What does your pool contractor/designer say?

Tell him the look you want to achieve.

He says keep it sharp, as does our deck guy and one other tile guy. However, two other tile companies (as well as the guy at the tile store) he has used forever say we want bullnose. :/ It’s just baffling to me how adamant each are about what to use and we are completely confused!

It's a beautiful setting. I love the desert.

So, the entire back wall will cascade down towards your fence into a catch basin? Or do you mean the spa and the raised upper curve portion to the left will have the water?

Given the fence, I don't think a negative edge pool, as I'm thinking of it, will be very dramatic...they look better elevated over open spaces.

I would do cascading water falls from the spa and the higher curved planter area on the left.

Yes...the entire back wall and the raised spa on the right. Actually, this picture was taken standing up on top of a wall...so it’s a funky angle. When looking outside our large window or standing on the patio, you can’t see the bottom stucco portion of the fence. Also, we may eventually remove a portion of the fence directly behind the negative edge and extend it further into the desert with no stucco.

I understand now.

Since you don't really see the waterfall on the back side, you could use bullnose. If you want a more dramatic waterfall around the spa, the tile needs to be sharper edged to throw the water out from the wall.

I think removing the fence behind the negative edge will give you a more dramatic look.