Honestly though, Dthrow is very much positional and character dependent when thinking about it vs Bthrow (his other combo throw, which often gets me Usmashes, Fairs, regrabs, Bairs, nairs, whatever based on my read). U throw is for killing and sending offstage, and IMO is just a better Fthrow overall as it does 5% more, kills way, way earlier, and in general even does a better job of sending offstage at lower %, Fthrow is really only useful at lower % when tossing somebody toward the other edge or something.
Zard's dthrow is great because of his tools out of it. It forces a tech chase situation on a character that is faster than marth with comparable grab range, disjointed sweeping moves along the ground in Dtilt and Dsmash, and low, hard hitting aerials in Fair/Bair/Dair to work with as well. If you catch somebody on a platform, chew them a few times and Dthrow and reap a free hit or regrab for as long as you want. Bthrow is more for a hard combo, but often only lands one other hit and maybe regrabs at low % on fast fallers. For controlling an opponent Dthrow is better.