I think David intended his voice to sound like it does on "Keep Talking" for a reason...look at the name of the song.
Gilmour's voice has suffered a bit as he gets older - some of the vocals on Pulse are strained (Hey You, High Hopes), but he still has that sweet sound. And I'd still take his vocals over Roger any day.
Roger's vocals have improved with age - I think he's trying harder to sing musically. It's unique, but it ain't pretty
Just my 2 cents.
