I have dozens of CD's from both David Arkenstone and Acoustic Alchemy, as well as many more from Foreplay, Dave Gruisin and Andy Narrell. As none of this material was ever released on LP, no comparisons can be made between the two formats, but just about all sound pretty good with some "outstanding" comments valid for the Fourplay, Arkenstone and Acoustic Alchemy discs.
More important, at least in my opinion, is the remarkable mastering done by Telarc on its many outstanding classical recordings. The former president and chief recording engineer, Jack Renner, knew how to use the digital medium, and his work shows it - rarely is there the "steely" sound of strings, or the harsh, "in-your-face" closeup feel of many other recordings. Jack is no longer with Telarc, but those whom he mentored are, and they are basically following in his footsteps.
I own well over 100 Telarc discs, and have to say that the best sounding of all is that of Vaughan Williams, "A Sea Symphony." Mastering was done by one of Jack's proteges, but it's the finest sounding CD I own, bar none. Anyone who thinks that CD's simply cannot ever sound good really owes it to himself to check out this recording. The orchestra sounds lush, clear, full, and above all realistic, and the chorus sounds better than any recorded chorus I've ever heard. That's saying a lot, I know, but this disc merits all such accolades.