Is the bag included with 70-200 f/4 IS USM...?
The F4 IS comes with a soft pouch, the 2.8 IS II comes with a rigid pouch.
To the OP´s question: From what I read the 70-200 F4 IS is sharper than the non-IS, additionally the IS will guarantee you sharp photos in low light conditions that the non-IS simply cannot meet, handheld of course. I have the IS and produces incredibly sharp photos event at F4 with a full frame (have not tested yet with a crop sensor). If the choice is between those tow, by all means get the IS without a doubt.
Regarding the dilema for more reach beyond 200mm, I pondered getting the 100-400 or 70-300 in another post but chose instead a 70-200 IS II (despite already having a 70-200 F4 IS that may get sold later) simply because I can put a 2x extender on it. So far I´ve tested both the 70-200´s with a 1.4x II and quality is very, very good beyond f6.3 on the F4 and beyond 5.6 on the IS II (and I have the 85L and both Zeiss Makro Planars to compare sharpness). Based on what I read the 2x will not be as good but very close to the 100-400 at 400mm (some say it is as good). I´m willing to give it a try but it must be with the new 2x III though.
To me, the overall advantage with the 70-200 IS II is complete flexibility:
- you can perfectly use both the 1.4 and 2x extenders
- you get fantastic versatility from that combo covering 70-400mm and still have 200mm at 2.8 when needed.
- Added bonus you maintain the 1.2meter close up focusing capability of the lens even with the extenders so focusing something at 400mm focal at 1.2meters should be interesting.
-resell value of the IS II is pretty good, specially if you buy it now that Canon has a cashback on it (at least in my country)
-Finally, when using this on a crop sensor you obviously get 1.6 times more reach but more importantly you can keep ISO on check cause even with the 2x you can guarantee f5.6
The penalty, go figure, is of course the added weight (which I confirm you´ll experince vs the F4 IS) and the fact the 2.8 IS II plus the extenders is the most expensive option, though it is modular as you can sell either the lens or the extenders later if not happy.