I have been flying a lot of short haul recently both with SAS (as Eurobonus Diamond) and with Finnair (as Finnair Plus Platinum), both premium and non-premium. I am fluent in both Swedish and Finnish and consider both as my home airlines. I think that I am fairly unbiased in making the comparison regarding the inflight service.

In premium short haul, Finnair's business class is clearly superior to SAS Plus (guarenteed seat block, better meal, nice and personal service, curtain, ...).

In economy/GO in short haul, both seem to be equally unpredictable/bad with free seat next to me (or "seat block"). Both have the perk of free drink with high quality options (champagne at Finnair, Mikkeller craft beer at SAS). Both have the same procedure when providing the free drink (the secret code, never say anything but do not charge). I have not needed to show the FF card for ages for any of the two. Otherwise I have never gotten any recognition at SAS, not a single time, while at Finnair the cabin crew often in a nice way welcomes me to the flight when providing the newspaper ("welcome to the flight", "nice to see you again" or something similar). I also like the Finnair cabins more than SAS, on average they are newer and feel more fresh and airy. The cabin crew on average seems more polite and nicer at Finnair and also seems to spend a little less time somewhere out of reach of the customers, talking with each other, knitting, reading or whatever they can to instead of doing their job.

So based on inflight experience, I do select Finnair for short haul for the reasons listed above, if both have comparable schedules and prices.