As others have suggested, it's not as simple as which cartridge. Stock fit, gun weight, barrel length, recoil pads, etc. all play a role in perceived recoil
Yes, and to this I'd add shooting position. With zeroing or testing the accuracy of rifles that boot a bit I make a point of setting myself up sitting upright behind the rest, or even kneeling behind the rest, rather than hunching down over it. That seems to make a bit of difference. You can also reduce the recoil considerably for zeroing by using a bag of shot between rifle and shooter, and I've helped a few out with this.
I've had a few rifles that really were uncomfortable to shoot though, at least at targets. I had a Mauser .30/06, with a narrow steel buttplate and narrow comb, which was quite unpleasant to shoot and left a hell of a bruise. My light little Browning .30/06 on the other hand is very easy to shoot, even firing rapid strings of shots, and I haven't found various 9.3s a problem either, including my own 9.3x74R.
Another I found a bit unpleasant was a Marlin 1895, when shot with full-house handloads. It was a pussycat with factory ammunition though. Even my Marlin 1893 could sometimes give me a wake-up, given its very narrow comb and buttplate.
On the whole I find that from about .30/06 up I prefer a recoil pad. I also would agree with those who say that you don't even notice the recoil when shooting in the field. That is my experience at least.
