I used to think of myself as the sit-up king. I started doing them when I was 15 years old, having been taught them at school (wrongly) and together with press-ups they were my key core exercises. I found sit-ups easy and could do 100s at a time, trying lots of fancy variations like elevated press-ups to reduce the number of reps before exhaustion and thereby avoiding the boredom and time, often with weights on my chest or behind my head. And then! Getting lower back pain in my early 50s led me to do some actual research and I realised that several military training programmes now eschew sit-ups because of later life back problems! Bugger!
Since I've stopped sit-ups (and do less office work/driving) my back has been considerably better. But I'd not ever considered Ab-rollouts!
I'm not sure of the relative merits of press-ups vs plank, perhaps one is a bit more dynamic?
Oh have I ever mentioned indoor rowingas a great core ex!