note: D3S 733 is Book One, not Book 2.
The WTC's were originally issued as single LP's (recorded between 1962 and 1972), so the 3 lp sets are by definition, reissues. My preference is for the singles. In general early Columbias are preferable to later Columbias. I'd say that if you go with the boxes, stick to the 2-eye version (gray label) for the first set, which again, is D3S 733.
D3M 31525 is Book II, and should be Stereo, it's just Columbia's numbering system changed in the '70's. As far as I know, Columbia's notation for Mono would be the letter L. For example, the Book 1 set in mono would be D3L 733.
The numbers for the first 3 single stereo albums are:
Hope this helps.