I used to think that illumination was mostly unnecessary but that has definitely changed from various hunting experiences that I've had. Early mornings, late evenings, even dark buildings all make it difficult to be effective in these scenarios without some illumination. With the light gathering capabilities of todays optics you really are handicapping yourself if you don't have illumination, in many situations.
FFP scopes with a broad magnification range are another reason to have illumination. The reticle is very small and basically ineffective at low magnification with most FFP scopes unless you have illumination.
Personally, I'm going to stick my head way out there and say that I value illumination over FFP as a feature, at least for the scenarios that I find myself in while pesting. For others that may not be the case because of their applications. The reason that I find FFP not so important is that with the superb tracking and precision of quality scopes dialing is effective and efficient. I'm amazed by how often I see people with FFP scopes using their turrets!
The only real world advantage that I can see FFP giving over SFP is when targeting rapidly moving targets at distances greater than my point-of-aim/impact distance. But even in this scenario, chances are that you are running at max magnification with your SFP scope and your reticle holdovers are now accurate(on most SFP scopes max magnification is where the reticle holdovers are correct) so that you can use your reticle exactly like you would a FFP.
Oh, shoot...I just convinced myself to buy a SFP scope.