I don’t use these in AV but have used an SPL meter for different scenarios to do with measuring SPL of equipment and spaces - so not so much at various frequencies which I assume is where you are coming from? Meters I have used are calibrated - meter and microphone seperately - but the calibrated input of those is suitable for the work. From memory is was say 95dB A weighting but the point is it wouldn’t suit AV work most likely. It and the calibration was all a lot more expensive than the RS meters as well I can assure you!
Sound is an analogue input so any difference between the digital and analogue readings is down to the quality of the components that change the input into the output.
A search shows RS SPL meters have been widely checked and digital or analogue provides a pretty basic level of accuracy that is close enough for pretty average setting up of audio gear. I’m not sure a comparison between the RS digital and analogue meters would show up anything that would make one better than the other given their underlying lack of calibrated accuracy (according to a myriad of forums and sites form a basic search about the RS SPL meters that is).