I picked up the Mingus titles whilst I was in Ottawa over Christmas, and Black Saint was the first thing I played when I got back. It sounds amazing - rich, ultra-clear, dynamic. The brass in particular are stunning - the tuba growls in this explosive and elephantine way that I don't think I've heard so convincingly on a record before. I think the mastering style of this Acoustic Sounds series suits these Mingus albums perfectly, more so than the Coltranes. Much as I appreciate hearing Coltrane's horn on ALS in greater clarity than any other pressing I've heard (I've not heard an original), I don't think the reissue is perfect - I still prefer some Japanese reissues in some ways, and the dynamics are not exactly right to me. But I may get over this. On first impressions though Black Saint is as good as I'll ever want.
I wasn't going to buy Mingus x5 because, as mentioned above, I have the AP 45RPM reissue, but there was a sale on at Legend Records so I went for it. I'll do a comparison eventually.