Except, is that how you rank prospects, by who’s more likely to make the NHL sooner? That’s not my view of prospect ranking...imo prospects should be ranked by their potential to be a better NHL player for the club....I put Blomqvist higher for that reason: he has higher upside to be a good quality starting goaltender....OConnor could make the team soon but his ceiling is as a bottom six forward, which are a dime a dozen players...
My personal approach is who's going to bring the most value to the org, and that means balancing certainty vs ceiling (and probably a bunch of other stuff). In an ideal geeky world I'd have a ton of comparables, and you could map what happens in terms of WAR for those comparables as worst cases, not great cases, average cases, good cases, best cases, and so on, and come up with a score like that... but I can't, so I have to eyeball it.
Blomqvist has, to the best of my knowledge, a very low level of certainty. Look at Jarry's draft as a quick eyeballer, and in the top 10 goalies taken, Jarry's the 2nd most successful player to date there with 62 games. Saaros leads with 118. There's only one other guy who might be a success (Hogberg). It's possible there's not a single long term starter among them.
O'Connor, on the other hand, is about to close as sure as we can get. He's got size and skating, he's got a decent amount of skill, he's done it at a good level of competition. It's a lot harder to gain the data for a quick eyeball, but my guess is the last 10 NCAA forwards touted at O'Connor's level yielded more than 2.5 NHLers.
So, for me, the sort of ceiling disparity (and likelihood of reaching it) I'm looking for to overlook that needs to be nearly as big. The difference between a good quality starter and a good 3rd liner isn't big enough for me. If Blomqvist was even maybe 1 year further along it'd be different... but he isn't.