I have the old GRP, but not the Heps. I find two Heps by Basie only ("Listen You Shall Hear" and "Do You Wanna Jump") plus a third with a lot of tracks by the Basie band sans Basie with Harry James ("Basie Rhythm") which nevertheless appears to have some of the Basie Deccas too. Are those the three? And is the sound really that much better than the GRP?
Likewise, is the Hep "The Jubilee Alternatives" also on the Mosaic Basie/Young? I don't think so, but I'm not near my Mosaics at this moment to check.
gregmo