OMG, a Dragonite vs. Salamence debate! I thought I would never see one of these again.
I'm a DNite fanboy through and through having worked a lot on testing for the 5th Gen Analysis. After using him extensively in both the DW and OU tier on every team I made with a variety of different sets, I believe a few things to need to be addressed.
First, Bulky DDNite is overestimated, if not overrated. It is insanely hard to get +2 on the Bulky DDnite simply because even with multi-scale, many things will still 2HKO it which means you have to keep on roosting. Many things can survive a +1 Dragon Claw and then KO Dnite if you have taken any prior damage while setting up the DD in the first place. This means, you have to have taken 0dmg + have a DD in to make the bulk worth the investment. Moreover, status is a huge problem for a bulky DDnite since it won't kill the status-inducer with a +1 DClaw any time soon. For example, the Jellyfish with WoW can easily stop a sweep in the making. In short, the metagame today is just too fast-paced to afford 2 turns to set up.
Contrary to popular belief, Offensive DDnite is not completely overshadowed by Salamence since you can more or less guarantee a DD with multi-scale even with no defense investment. However, multi-scale does not force switches like Intimidate does due to the one-turn-use nature of the former. This means you should only set up on something which you know you can OHKO (usually with Outrage) after a +1. It also means you're very hesitant to switch in Dnite against an attack in the first place, instead preferring to send him in after a Pokemon has fainted so multi-scale can remain intact. The plus side is that Dnite can set up on special attackers as well as physical ones due to the broader protection multi-scale gives. Finally, the lack of speed is still ultimately reason why Salamence should be used in the Offensive DD position. However, I've been having a lot of luck putting ESpeed on my offensive DD which just destroys any Mischievous Heart users (except Sableye) and weakened revenged killers in the late game.
CBNite is still the best set for Dnite in my opinion due to the immediate power it brings. In this fast-paced meta, it's hard to even find time to DD once, so having a CB opens up so many options. With multi-scale, you can almost guarantee Dnite will launch at least one attack since sand + hail does damage at the end of the turn (assuming you sent Dnite in to revenge something). Sure, a physical wall can stop it, but this gen, most people use Nattorei, which does not have a recovery move. Thus, you can keep pounding it until it breaks. In fact, this is the current strategy I'm using in conjunction with a Specs Latios. Those two combined break through so many walls with limited to no prediction. Of course, CB ESpeed serves as an excellent revenge option, even against Dory.
Lastly, I just want to point out that Stealth Rock, while still a major concern, is not an automatic death sentence for multi-scale. Decent use of a MM pokemon (which serves other purposes as well) can ensure that it's not on the field more often than not.