What matters more?? CP/IV Percentage or Stats??

Big booty girls in short shorts or big boobie girls in wet white tees?

Depends who you ask.

The biggest factor for me is how much stardust will I need to sink into it. The lower its level, the more I scrutinize each IV. If I catch something at a high level with a perfect attack IV and low others IVs I'll still use it since attack is more important for raid breakpoints. I once caught a level 33 Beldum and a level 35 Machop with perfect attack and single digit other IVs and still evolved them due to the minimal dust cost - had they been lower than level 30 I doubt I would have kept them.

As an aside, both of your Garys are still powerful. One of the first things I powered up to near max was a Gary with the same IV spread as your first one.

Dare I say neither?

MOVESET

For example, I'd take an average Machamp with DP over a perfect with any other charge move.

At the same level, the pokemon with higher CP is better. It may not have better IVs using traditional methods, but it will have better IVs if you give the attack IV double weight.

The attack IV is worth as much as the defense+stamina IVs combined. Ultimately, if you give the attack IV double weight, then higher CP = higher weighted IV.

Appraisals are great for identifying candidates for good pokemon, but you'll need a calculator to know for sure. Although I rarely get enough 80%+ pokemon to need to choose between multiple amazing copies.

Moves are most important, but can be changed with TMs.

Having a high cp Pokemon is battle ready and can be used with little, or no investment, regardless of appraisals.

However, I would only spend resources (TMs, stardust, candy) powering up, or changing moves on high IV Pokemon.

Attack strength is the one most people ultimately concern themselves with.

So, to sum up.
Moves are the most important in battling, catching high cp Pokemon is great to use and throw away, or to fill out battle squads for raids, but only actually power up strong high IV Pokemon, for the long game, they'll be better in the end.

You can just check what is the CP of your mon at lv40 and compare it to the maximum CP it can get at lv 40 100%.

The more I have played the less I think IV really matters much.

In gyms and raids with lot of people it could not matter less.

Shortmanning raids, it could theoretically have an impact, but I have seldom seen it in practise. But the opposite, a team with 93-98% Machamp beat a team full of 100%´s in damage against a Tyranitaur, I have seen a couple of times. My conclusion is that it very rarely matters.

PvP? Most people I have discussed the subject with see PvP as the coming triumph for 100% collectors. I doubt it.
If PvP is implemented in a way similar to gym/raids (just tapping, no skill) it might be so, but that kind of PvP would be utterly uninteresting. You could just compare CP numbers and proclaim the winner from that. I really hope for something better.

As for the ever present quick move "break points".
I see they have a theoretical value especially when solo/shortmanning. But in reality, and what would you prefer? Using stardust to take a lvl 20, with 15 in attack, to lvl 37, or taking a weather boosted one with 13 in attack from lvl 34 to lvl 38 to reach the same breakpoint.

Base stats, typing, move set and level have a big deal of impact, the order of importance vary. IV almost always come last, with the exception of really weak pokemon (Shuckel :-)