If I were you, I'd probably do Kenny Drew's Undercurrent for the following reasons (I don't have any of the albums mentioned although I do have "Soul Station" on order from MM, so take my advice with a grain of salt):
1) the best comparison for you might be Blakey's "Big Beat" as you have two originals of that, but I've read that the recording is a bit "hot" on that one with the MM so I'd kind of expect the original to be the same. It might not be the best comparison in light of original sound quality of master tape, although a MM to original comparison would be interesting-I can recall reading recently here that someone preferred a Parlan original to the MM.
2) the Drew, on the other hand seems to have had favorable press with respect to sound quality and you have a King of that. The King's have a reputation for being about as close to the originals as anything (much more so than the Toshibas) and are also still available on the used market for around $50 or less so I figure a head to head with a King is a good and fair comparison as you can buy either for around the same price, which you cannot say about many of the originals.
3) I would really hope that the MM would be significantly better than a Connossieur, but who knows?
As to the mono/stereo issue, I'm sure you've read the story. Those MM's released in mono are supposed to be original mono master tape; everything else in stereo is supposed to be original stereo tape and if that release came out on BN as mono it is supposed to be a fold down.
1) the best comparison for you might be Blakey's "Big Beat" as you have two originals of that, but I've read that the recording is a bit "hot" on that one with the MM so I'd kind of expect the original to be the same. It might not be the best comparison in light of original sound quality of master tape, although a MM to original comparison would be interesting-I can recall reading recently here that someone preferred a Parlan original to the MM.
2) the Drew, on the other hand seems to have had favorable press with respect to sound quality and you have a King of that. The King's have a reputation for being about as close to the originals as anything (much more so than the Toshibas) and are also still available on the used market for around $50 or less so I figure a head to head with a King is a good and fair comparison as you can buy either for around the same price, which you cannot say about many of the originals.
3) I would really hope that the MM would be significantly better than a Connossieur, but who knows?
As to the mono/stereo issue, I'm sure you've read the story. Those MM's released in mono are supposed to be original mono master tape; everything else in stereo is supposed to be original stereo tape and if that release came out on BN as mono it is supposed to be a fold down.