Yes, those two Dragonites will be equal in strength (assuming the same movesets, of course). The only time IVs really matter is when you're comparing two pokemon of equal level - a 100% IV Dragonite at level 30 will have a higher CP than a 25% IV Dragonite at level 30, and will be a better overall fighter (still assuming the same movesets). Another way to think about it is that CP reflects the current combat ability of a pokemon, while IVs represent the maximum theoretical combat ability of a pokemon.
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Are same pokemon species with different IV, different level, yet similar CP equal?
So if you have a dragonite who's like level 25, 3000 CP with good IVs vs. a dragonite level 29, 3000 cp but with poor IVs gonna be equal in strength? In other words, is CP a good measure of overall strength to compare these two pokemon