I don’t see why you would limit yourself to either one of them. A resource-cost, cool down, team-wide limit, diminishing returns etc they’re all very important measures required to balance the game. These limits are what allows a developer to do more extreme and crazy things after all.
What I would like to see more of however, is ways to replenish your resources. This only heightens the skill ceiling and the potential strength of a player. There can be all kinds of interesting ways to generate energy, it should be easy and it shouldn’t be common, but if it’s at least possible then players can start ramping up their power and become true monsters in the field.
I’m thinking of replenishing energy through scoring killstreaks, through leeching it off corpses, leeching it off incapicated players, through supplies, through player auras, from vehicles etc.
You can include numerous ways of replenishing energy if you make upgrades a prerequisite for them. That way you get some players using kill-streaks as a resource gathering while others garner it through corpses, depending on the way they decked out their player characters.
It gives a lot of variation in specialisation as well. Some players may chose to start with a large maximum capacity of energy, some may chose a fast passive generation and some may search it in active generation while there may be others who go for a very energy-economic build and put their strength in other things like raw combat power, or stamina.
If you allow for more ways to generate a whole new level of depth opens up.
Plus there’s just nothing more satisfying than ascending ordinary combat potency through stacking up your cards in your favour through clever play. All in all it’s hugely rewarding the cerebral playstyle without impeding on more basic approaches.