I wanted to give a quick summary about how I feel on each of the four moves discussed so far.
Jab
This move is great when you need something fast. It's nice to have at least one option for a quick attack to throw out at times, disrupting most things the opponent might try to do. I use this move as an occasional follow-up to dthrow, though be cautioned that it's easily escapable. Another great use is to randomly throw it out there for some damage. You can continue to hold it if they stay in the pump or let them go.
U-tilt
I rarely use this move. It might be because of personal reasons or that I think it's just too risky. The startup is miserable and the follow up isn't anything more impressive then simply short-hop nair off the ground. Idk. I could see arguments for/against use this. I recall Vinnie loved using this.
F-tilt
There are two important things to note about this move. The ending lag is horrendous and the startup time (hits on frame 10) is shorter than any of your smashes (hits on 15-18). Because of the first, I would recommend against using this move. Fsmash/Dsmash are much safer options. The short startup time is the only reason I'd consider using this. When you need something to come out sooner than an Fsmash/Dsmash, use Ftilt. It takes some understanding, and a great deal of practice missing with the smashes, to realize when the tilt will hit. Again, I use this rarely.
D-tilt
Easily the best attack out of the four list. This move not only offers us an infinite (use against walls) but it's a great zoning tool with high priority. We all know how great our bair is right? Super hard to beat. Well, dtilt does the trick. It's that good. A well time dtilt can put a halt to most moves in the game as well as many projectiles (like against TL). If you want to test the power of dtilt, try playing a match where you main focus is to use dtilt more than any other move combined. Spam the crap out of it!