Big IV differences when preparing for PvP

You've heard wrong. For CP-limited leagues, you want a low attack IV, not a low IV total. This is because attack stat matters more in CP calculation, so pokemon with low attack IV can squeeze in more total stats while staying under the CP cap.

The optimal IV spread depends heavily on the pokemon, and for the most part anything that hits between 1495-1500 tends to be pretty decent for great league. You need to use a dedicated stat product calculator to find out what IVs are the best, but in your case both have pretty even IV spreads and hit close 1500 so there isn't going to be much difference between them anyway. I recommend picking the one that takes less powerups.

Generally speaking, because attack is weighted in the CP formula, higher defense*stamina is more important. An IV distribution with low attack and high defense can help push a few more points into defense.

If you are wanting serious min-maxing, look for one of the PVP spreadsheets posted on the SilphRoad reddit. You can input pokemon species and IVs, then it can output the closest level and CP under the CP cap and show the calculated attack, defense, and stamina stats to compare with other IV combinations.