Multiple attackers of the same mon or diversity?

I prefer diversity but at the cost of most likely not being able to solo a lot of T3s. Although different form mons (shiny, gender) are included, just no more than those. But if you really want to win at all costs, multiples of the same type are ideal.

If you really want diversity then go and power up that zapdos, the Attack is 15, so you're not really losing a lot of potential.In my case i got a 91% 15a/15d/11s raikou, now lv 30, and a 15a/15d/13s zapdos, now lv 23(waiting for candies), and both are pretty good. I prefer having a lot of differents attackers than many of the same.
TL;DR: It's personal, but i would power up that zapdos.

While I would prefer diversity, you're sort of forced to go with the hand you're dealt. My only 90%+ IV legendaries are one raikou and two entei. The others I have aren't close. When all is said and done, I might power up both entei

I prefer diversity, if not in mon, then in movesets. For example, I have maxed out 2 dragons. One has DB/Hu and the other has DT/O. It adds to my personal enjoyment of the game.

Diversity 100 percent.

I would go for diversity. Two of each at most unless i get 100% for my third one. But powering my third one is mostly because i am vain;)

Diversity, and Zapdos will STAB counter Ho-Oh with SolarBeam (Which slays literally all of its counters at super effective damage with the exception of electric types) with its additional resistance of Grass Moves