First things first. Make sure you and the pool builder are talking about water depth and not wall depth. There's been a lot of mix ups in the past where builders and owners have different thoughts. If you want 9" of water, then the wall has to be 12". Want 12" of water, then the wall has to be 15".
We have 12" of water on our ledge and I wouldn't want any less. The only problem with 12" of water is the Ledge Lounger would have to be the Deep Ledge Lounger style or a riser would be needed for the regular one. We did the risers, and with 12" of water, it's hardly noticeable.
Also, Ledge Lounger sells "seconds" that have minor blemishes on them, and we got two of those and there's nothing but a couple scratches on the sides that we don't see when in the water. I think they were about $150 off regular price. I did receive an email from them recently, that states that they had to raise their prices for the first time in their history.
As for comfort, we have head pillows for them, which makes a huge difference in making them more comfortable.
If you're still in the planning stage, make sure the length and width of the ledge will accommodate the loungers you want to put there, and still have enough room to move around. Ledge Lounger website has documents that give minimal space requirements.