I'm so sick of these sorts of questions.
First of all, no one is better suited to answer this question than you. You have all the information you need, why do you think someone else should make the decision for you?
Secondly, unless you already have 125 Dratini candy, and are ready to evolve twice into a Dragonite, why do feel the need to make the decision now? By the time you get the candy, you may have a better option.
Third, do the basic math yourself. However, because I have the spreadsheet right in front of me, I'll do it for you: It will cost you 56,600 Stardust and 61 Dratini candy to power up your level 5 to max (level 22.5).
No one can decide if that's worth it but you. If you don't catch many Dratini, then all that extra candy just for a few more stat points obviously isn't worth it. However, if you are drowning in Dratini candy, and you like the personal satisfaction of 100% IVs (cross your fingers you get a good move set), then go for it.
TL;DR No one can answer this question better than you can. Do your research and make your own decision. Don't ask pointless questions because of a need to seek validation from total strangers.
