They are, but where the slam record is very close, those other factors are important, too. I think Murray's career is clearly better than Wawrinka's and that's only partly because he's been to the later rounds of slams much more often (*), and also because he's done much better in other events.
* Note: as well as the question of slams v everything else, there's also the question of winning alone versus getting to later rounds. Perhaps for Djokovic and Federer, there's a case that being runner-up doesn't matter much, but at the level of Wawrinka, Murray, and Medvedev, I think that getting to semis and finals adds something. And I think that's one reason Medvedev seems closer to Wawrinka than the 3-1 slam title count suggests: Medvedev leads 5-4 in slam finals reached. It doesn't overhaul the 3-1 title deficit, but it does narrow it a bit.