Imagine that we've got a couple of gates open and every investigator has 3 clue tokens. All other things being equal, is it better to try to immediately attempt to close those gates or would it be better to save up to 5 clue tokens in order to seal them? By better, I mean more likely to result in the investigators winning the game.
It depends. Mostly on how likely a gate is to open again at that particular location.
It's better to wait and seal gates with lots of gate mythos cards in the deck, to prevent them from continuously re-opening.
It's better to quickly close gates with few gate mythos cards and many clue mythos cards, as it will be unlikely to open again, and blocking access to valuable clues while it sits unaddressed.
The specific frequencies can be found in this document.
I think the document on "Gate Seal Priority" was a little bit misunderstood. It seems to be meant as advice on which gate to close, given that you HAVE TO close a gate.
The biggest drawback with closing gates as opposed to sealing them is that if they reopen, a new doom token is placed on the doom track. In my group we ALWAYS save up and clues and seal games unless the "gate limit" is very nearly exceeded and no-one has enough clue tokens tokens. In this desperate instance, the document on "Gate Seal Priority" is a great way of determine which gate to close.
Even when playing with expansions that has the "gate burst" rule(gates open even when sealed), we always seal. This is because gate bursts do not put new doom tokens on the track.