[PvK]

Originally posted by HotNifeThruButr:
... I would also give the Infernal forces series - I know this applies to Frost Fiends, but I haven't looked into the others - more bang for the buck. Right now, summoning a single demon is more economical than a horde, and time shouldn't be the only thing saved in such an advanced spell.
...

In general, I'd say that it's interesting to retain a trade-off even after the more powerful spell is researched.

PvK