Actually, there are a few FF in which Summons actually give you a real advantage in battles. In FFIV, FFV, FFVI summons were pretty much pointless to use in battles, especially in FFV and FFVI, since you got so many more options, which were less MP intensive for the same results. In FFVII, summons were pretty much pointless too, except for KOTR, which i never used too, even when battling Ruby and Emerald.
FFVIII pointless as well, albeit for the excellent junction and GF abilities, but in battles they weren't that useful, unless you worked a strategy around the extra HP they gave you when you summoned them, which in FFXII can work in the same fashion, using the espers as meat shields.
FFIX pointless, and you only begin using them from the middle of the 2 CD forward....
FFX had a good summon system with the Aeons, but once you've got most of the sphere grid unlocked, all other abilities would surpass summoning, plus only one character could do it, so it's a major downside.
My point is that, if you base your strategy solely on summons, then you're outlooking at so many other efficient layers of strategy that each FF game offers.
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