Why not both? Get a patchable for your basic functions, then build up a skiff or two (or three, four, etc) with more esoteric things. For eample, a Plankton ANTS! would be nice and cost-effective, but just dropping something like Happy Nerding's FM Aid in that mix to tamper with the ANTS!'s VCOs and allow TZFM makes that $599 box WAY scarier for just the cost of that one module! Add several more, and that simple little patchable can turn into a holy terror for not a pile of cash.
This is sort of my plan for my Digisound 80, actually...adding patchables to build it up, for cheap, into a (rather portable!) monster that cuts the mustard for both studio and live use. Other stuff, certainly, will come along later...but being able to add two of those boxes plus, say, a Modulor114 and a Keystep (on hand already) will turn the original 22-module Digi into something capable of some major sonic heavy lifting. Just an example...