I should power this up?

I would say power it up, if you can spare the dust. Given that dratini candy are rare, risking a 1/6 chance of getting that moveset again doesn't seem worth it.

depends on what you will use it for. If your thinking of using it as a defender go for the 91% dratini. My area also doesn't spawn dratinis but it's really easy to get from ten Km's approx. 1 in 3. If your going for attack and you have good stamina go for your current dragonite.

that moveset is really good.
elolving another will be a risk for candies

Depending on how competitive your gyms are I say level it up. In fact there are almost no scenarios where this isn't your best option if you also want an offensive monster.

Power up the wild one. DT/O is currently the best moveset you can get, and the IVs are fine. Even assuming worst distribution (3A 15D 15S) it still has higher max CP than anything other than Tyranitar or a better Dragonite, so it'll still sit near the top of gyms.

If it should ever sit at the bottom of a gym somehow, then you can just use it as an attacker.

With 84 candies, right now you could take it from level 12 up to level 28, where it would have about 2770 CP, whereas the Dratini requires 189 candies to evolve and get to level 30 - 125 to evolve, you get 1 candy back for each evolve, and then 66 to go from level 20 to 30.

So working on the Dratini costs about 90 more candies, and most likely have a worse moveset, but it'll have about 80 more max CP, which isn't that big of a deal, because like I said earlier, your Dragonite still tops everything else with perfect IVs besides Tyranitar and other Dragonites.

First off, congrats on the catch!
You have a fairly good IV Dragonite with the best moveset, both for offense and defense. Of course power that thing up!
The chances of getting the same moveset from evolving your Dratini are fairly slim (~16.67%, to be exact)...