If you are staining/finishing the doors, veneered doors have to be re-finished carefully. Once the finish is stripped, the veneer has to be carefully sanded so that you dont cut into the laminated layer beneath. Veneers are a series of laminated plys similar to ply wood w/ the last layer being the desired species. veneered doors can pull lose at the veneer, but is rare i would think. It all comes down to the quality and reputation of the door mfgr. Warpage on solid wood doors shouldn't be an issue if sealed/finished properly, but can happen, again, i would think it would be pretty rare for interior. As far as sound control, no advise there.

A solid core flush door is solid all the way through but it might have a MDF or lumber core with a veneer. It's difficult to know how to respond to questions about doors without a description of what they are. They could be solid or veneer wood for a natural finish or MDF. They could be flush or paneled. They could be 1 3/8" or 1 3/4" or thicker. The best value IMO is TruStile made in Colorado. Very nice doors and the web site is full of information and easy to use unlike JeldWen, Masonite or Simpson. The Door Design Tool is fantastic. Here is a link that might be useful: TruStile doors

My thought is solid wood in bathroom is not a great idea. But I have no basis for that. I am switching out all my interior doors to be solid and I was convinced to go with composite vs. solid wood due to warping, etc. I grew up in a 1910 house with solid mahogany doors and they did stick with the seasons so I was inclined to believe my contractor. I went composite for all solid doors. Cabinet doors might be a different matter but for Sure I wouldnt try solid inset doors in the same room as a shower.

I've looked at Omega-Dynasty, Medallion, KitchenCraft & Neff. The solid wood doors, in slab or otherwise, all show seams, or strips, of wood. I've been told the "strips" is what identifies the door as being a solid piece of wood vs veneer. So I agree with you. The veneers have a much more uniform look without the "strips" and if it matters to someone...the door front and drawer front can have the grain running in the same direction or not. Right now, I'm leaning towards doing a slab veneer front with a plywood box. I don't want to deal with warping issues later on down the road and in a slab door I like that the veneers do not show the "strips". My kitchen cabinets are all wood as the humidity is not an issue in the kitchen. Trying to get unconfused!!