70-200 f2.8 non IS or 70-200 f2.8 IS version I for weddings/portraits

[neuroanatomist]

Overall, the non-IS version will deliver a bit better IQ. But...a shot blurred by camera shake will have bad IQ. So...how important is IS? You've rented the 70-200 II before - I'd say look over your EXIF of shots with that lens, with an eye to shutter speed. If you're often shooting slower than 1/200 s at 200mm, etc., then you're benefiting from IS and the original IS version of the lens is likely a better choice for you.

As for weather sealing, the 5D isn't a sealed body so unless you're planning on moving to a 5DIII that's a lesser consideration. Still, I suspect the IS lens will be a better option for you.

[Sean Setters]

I'd agree that the IS version is likely a better fit for your needs--image stabilization is huge help when trying to hand-hold a camera in dimly lit churches. That said, you could get the same benefit by using a monopod with the non-IS version, but your mobility would suffer.

[Mr.Magic]

@w349: indeed weather sealing, didn't think of before but very, very useful

@neuroanatomist: when the 5D3 becomes less expensive, I'm indeed planning on buying it.

Does anyone have experience with these lenses in the field (or with both of them). I really love the IQ from the IS version II, but I can't compare it to the two lenses mentioned here, which are said to have a lower IQ. Should I be afraid I will be dissappointed or just go for it ??