Sort of related question: In what situations do you want to d-tilt with Link rather than d-smash, and vice-versa?
If memory serves, dtilt is like frame 12, whereas dsmash is frame 9. So dsmash is faster.
Dtilt has a little less endlag, so I vastly prefer dtilt for edgeguards (if it meteors, a misspaced meteor cancel = up+b semispike [or grab ledge or nair them] and missed cancel is death) because if you hit the upward launching hitbox on dtilt or any part of dsmash, they have similar launch angles but you can follow up after dtilt faster (I think).
Dtilt is somewhat safer on shields if you use the front part, dsmash is safer than dtilt if you hit the back but only slightly [I believe it's -15 and -9 for dsmash vs -11 for dtilt]. Note that if you dtilt a shield at range, a wavedash OoS punish isn't possible, since it takes at least 14 frames for the fastest if I can math correctly [3 frame jumpsquat, airdodge frame 4, frames 5-14 you are in landing lag]. However, you can be punished with things like Marth fair even if you space (regardless of your choice) so neither is particularly safe.
Dsmash covers both sides, so you can cover tech rolls beautifully with it (go to about 7:17 in this video:
https://www.youtube.com/watch?v=CKxQo7EzPRc where I cover both missed tech and tech roll behind with dsmash) [if you watch the whole thing, I've improved some since then and also got super cocky when I took the 2-stock lead and played really bad 3rd stock game 2]. Dtilt can cover tech in place and missed tech in a similar manner so it's often a decision thing, but dsmash CAN cover tech in place and missed tech if you vary timing (I think), as well as techroll behind. But again, more endlag if you cover missed tech with it (Though the speed may be what you need).
There's other stuff I'm sure, but I think these are a few good things to start with.