Just a note...Devas and Planetars can only be summoned with ToB installed.
POSSIBLE SPOILERS AHEAD:
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On that note, yes, I prefer the Devas and Planetars best. Efreeti are good against cold-based monsters (turn one loose in the "cold room" in Planar Sphere and have a field day!) Hakeshari and Nishiruu are great against enemy spellcasters. Still, some low-level "fodder" like wyverns, ogres, gnoll elites, hobgoblin elites, etc. are great against boss "baddies" like Firkraag, Thaxxie, and even Irenicus in the final battle. It's why I always keep a charged-up Wand of Monster Summoning around...always comes in handy.
-Sazerac