The differences and similarities of m-drol and M14add lie in their inherent characteristics and structures.
M-drol (superdrol) is a DHT based steroid. Meaning it has a similar structure to dihydrotestosterone and methyl-dht but is manipulated in certain positions to bring about a new steroid. In this case, it differs by the 2a and additional 17a methyl group; so you can consider it 2a, 17a methyl-DHT. M-drol (as i'm sure you know since you've ran it) is a very dry compound, because it's structure prevents estrogen conversion(on paper at least).
M14ADD (methylated boldiol) is a testosterone based steroid. It is essentially a derivative of boldenone with a methyl group at position 17 of it's 4 ring structure. It is also purported, as a diol, to be a prohormone or convert into Dianabol; The rate of which is unknown. It is a "wet" steroid, because, as a testosterone base (w/o a 4 chloro or other AI alteration), also converts into an estrogen(M-e2 or e2). Gains from this are heavy and fast, as you can see
here.