well 1 ad converts by some unknown mechanism to dht it is known to be quite androgenic so is probably pretty hard on hair. I dont lose hair on 1 -test but I know many who do.
4ad converts to testosterone which in turn can convert to dht, this conversion is bia a known method and can be blocked using finasteride or another anti-androgen. 4ad probably converts into only a few miligrams of dht per gram of 4ad since the conversion to test is so low anyways. Chemically 4ad should not directly convert to dht so i would have to say 4ad is the safer of the two on the hairline though not as safe as 1/.4 ad