I think RDR has plenty of ways to win this and I hope he does. I'm a fan. That said, I'm picking Rob.
I feel like maybe there's been a bit of an over-correction here, on two fronts:
1.) Rob's record lately hasn't looked so hot. Ever since Izzy 1, he's basically been trading wins and losses. The narrative is easy to build that he's in the twilight of his career, washed, or otherwise on the way out. But those losses have been to absolutely elite guys. Adesanya, Dricus, and now Khamzat. Every time he took a step down in competition to play gatekeeper against the likes of Cannonier, Gastelum, Vettori, Costa, Aliskerov, etc. he looked good. He might have a moment of danger where he got clipped in some of those bouts, but for the most part he outclassed those opponents and showed them levels. RDR is yet another step down in competition. He had a good run in ONE, but a lot of those opponents he beat over there likely wouldn't even rate the Top 30 in the UFC. GM3 and Holland are decent names, but perennial fringe Top 15 gatekeepers who have never managed to put together any sort of sustained success. Bo remains a totally unproven prospect. Ask yourself what Whittaker would do against any of those same guys. Meanwhile, do you see RDR winning the belt? Beating Khamzat or DDP? I don't. I'm not even sure if I would pick him against a prime Izzy, though I probably would.
2.) People saw Rob get taken down and submitted by Khamzat. Before that, he got outgrappled by Dricus. This has led to people saying that his ground game is trash or stuff like "Rob's elite TDD was always a myth because he stuffed Romero a few times!!!" I think maybe there's a kernel of truth to this insofar as fight fans -- myself included -- sometimes made the mistake of talking about Whittaker like he was a Middleweight Jose Aldo. That being said, Khamzat is arguably the best primary wrestler in the UFC right now and has an oppressive top game that managed to capitalize on Whittaker's injury (still a legit win). DDP is a well-rounded champion who has surpassed all expectations. Both men are freak athletes with explosive takedown entries and a good ability to win scrambles. Rob getting outgrappled by these two studs has made people forget, I think, that he's typically pretty good at keeping that from happening to him. Vettori, Gastelum, Romero, Jacare, and Brunson all failed to impose their grappling on him over the years. Aliskerov... never even got the chance to try.
I think it's important to remember that RDR is not a guy who shoots explosive blast doubles to bowl over his opponent. He isn't all that great of an athlete. He's a dude who plods into the pocket and reaches down for a lazy single leg... or forces the clinch to use his Judo. Even with RDR's advantage in size, I don't think that approach will play well with Rob. I expect his athleticism advantage to really show in stuffing the takedowns outright or at least allowing him to scramble out of some bad positions. Not to mention his ability to control distance and punish lazy entries with footwork, straight shots, and check hooks. RDR is slow, stiff, and robotic on the feet. If we're being honest, de Ridder is incredibly hittable and I think Whittaker will capitalize on that at range while sticking-and-moving. RDR's chances improve immensely if he's able to first hurt Rob in the pocket or in the clinch with a strike before forcing a grappling exchange, but I just don't see it happening more often than not. I think Rob picks him apart to a late TKO or a Decision win... but again, RDR is live and I'll be rooting for him regardless.
