I don’t think it will be all that different. When erect, the circumcised & uncircumcised penises look pretty similar, but you will notice the difference when not erect. When flaccid, the ‘head’ is usually not visible, it’s covered by the foreskin, which was removed if circumsized. I think it was a good idea for this guy to ‘alert’ you, though, just so you’d know what to expect & not be ‘freaked out’ & spoil the moment. I don’t think you’ll feel much (if any) difference during intercourse.