The Blakey has three bonus tracks — one alternate, and two tracks from a different session ("Off The Wall" and "Theory of Art"). Make sure to also check out SICP 4027 — Art Blakey's Jazz Messengers Play Lerner & Loewe — as this has some burning Johnny Griffin on it, and it has SIX bonus tracks. For the price, both Blakeys are well worth it.
The Mulligan is a very subdued, mellow session. Well-recorded, however, and the added conga is a nice touch.