2 bar vs 1 bar moves

Because blindly looking at DPS numbers is wrong, when you should be looking at the overall DPS from using a combination of quick moves and charge moves. You can't use charge moves on their own, because you need energy, and you get energy from using quick moves.

Usually 2 bar charge moves do more total damage compared to 1 bar charge move over a longer period of time, and moves that use more time have more weight on your overall DPS because it means your quick move makes up a lower portion of your overall damage (which is good because your quick move is your lowest DPS move)

For example lets say you have 1 quick move that does 10 DPS and you've got 2 charge moves, 1 that does 20 DPS over 2 seconds and another that does 18 DPS over 6 seconds, and it takes 6 seconds of using your quick move to get to 100 energy.

If it takes 6 seconds of quick moves to get energy for your charge move, then your overall damage is 6 x 10 + 20 x 2 = 100 damage over 8 seconds, or 12.5 DPS.

The 18 DPS charge move would instead deal 6 x 10 + 6 x 18 = 168 damage over 12 seconds, or 14 DPS.

The lower DPS charge move increases your overall DPS more because you're using it for a longer period of time, so it makes up a bigger portion of your damage, hence why Cross Chop is dogshit. It's the weakest 100 energy move so it has the least effect on your overall damage than all the other 100 energy moves that deal more damage but over a longer period of time.

Using an exaggerated example, lets say you have a move that has 1 damage and has a cooldown of 0.001s. This move technically has 1000 DPS, but it won't do anything to your overall DPS because almost none of your time is spent using this move.

androgynous has provided a rather extensive analysis of damage calculation.
I'd like to add the point of incomplete cycles: damage formulas assume full cycles where the charge bar is charged completely and the charge move used in one cycle. However, in real battle this is rarely the case. Either the opponent faints before the bar is fully charged or the last charge move is overkill and a weaker (one bar) one would have been sufficient.
It is easier to fit a whole number of complete circles in a fight when you have a two bar charge move than if it's a single bar charge move.

I see it like this: let's say Fire Blast does 100 damage and Flamethrower does 60 damage. Since Flamethrower is 2 bars, it does 120 damage in total rather then 100 damage Fire Blast. Therefore i would always choose 2 bar moves over 1 bar moves. Exceptions do apply for me such as Solar Beam.

Well, another main advantage for 2-bar charge moves is less energy wastage as compared to 1-bar move, especially if u dodge. Moreover, many might not be aware that u also gain energy if u take dmg from opponent.

So assuming in a 1-bar move, whereby u don't unleash it immediately, but wait til the opponent does it's charged move, in that interim, u are not gaining energy from both ur primary attack and dmg taken. For 2-bar moves, in the same scenario after the 1st bar is charged, u can still store the energy for the 2nd bar while waiting.

Interestingly, the energy gain from taking dmg can affect the dps. See this vid ( https://www.youtube.com/watch?v=Akxhn7gaT5s ). The vaporean's dps is very close to the 3 dragonites, and one of the contributing factor is that in that battle, the Snorlax only unleashed 3 body slams for the dragonites, but 5 body slams on the vaporean.