I played my first good DDD a while ago, and I'm calling 60-40.
A good DDD will ignore his lack of a chaingrab and focus on building up just enough damage to knock you offstage with Fthrow or Bthrow. From there, Falco's hilariously bad recovery gets the crap kicked out of it by DDD's multiple jumps and awesome Bair.
That being said, if Falco can chaingrab to the edge at any point in the match, it should be a stock. He's a huge, easy-to-spike target, and his jumps don't bring him back high enough to not have to use his UpB. So chaingrab, spike, and wait for the UpB. When it comes, wait until he gets to the peak of his jump, where he no longer has super armor, but doesn't have a hitbox yet, and spike him again. Of course, expect him to cancel it at wierd times to mindgame you, and plan accordingly.
As you can see, both characters are capable of, and will likely be gunning for, low-percent kills. Falco has the advantage in this regard, since his is almost guaranteed in the hands of a good Falco, stems from a single grab, and doesn't need percent tacked on previously to become viable.
If neither character can get an early kill, the stock will move slightly into DDD's favour. Falco has enough trouble killing as it is, so now that his opponent is one of the heaviest in the game and has multiple jumps, you can expect DDD to live to some insane percents. On the flipside, all DDD still has to do is get you offstage and beat the heck out of you with minions and bairs until you get KO'd. On-stage, minions, RAR bairs, fullhop dairs, and ftilts all beat out SHPhantasm handily, effectively eliminating one of our most useful spacing tools.
All in all, I still give Falco the advantage. Chaingrabs being essentially a free stock is too good, and he can more than hold his own in the later stages. Falco's laser game doesn't care about Waddle Dees and Doos, and Gordos travel so slowly that they can be reflected on reaction. In close, Falco can string together some nice 'combos" with Utilts, Nairs, Dairs, Jabs and Grabs. You just have to play smart, not let DDD outspace you, and don't get grabbed near the edge. 60-40 for Falco.
I personally recommend Smashville as your go-to stage against DDD. It's nice and flat, so you have plenty of room to Laser DDD into oblivion, and the simplicity of the stage means you can punish him any time he needs to use his UpB. Plus, the moving platform can arrive at some pretty opportune moments to bail you out when you're trying to recover against a wall of DDD Bairs and flying Waddle Dees.
