Personally, I value all migrants. If they bring new and useful[1] skills, I set up the industry with which they serve. If a precursor process is needed to give them work, then I use one of the newbies without a currently useful job (or an original settler currently idle, or the guy/gal themselves who can't do anything yet) to get that up and running.
If they bring a better skill than a current member, I'll consider deposing their predecessor (or doubling up, if the industry can stand that, as I might if they were just a bit below the current expert).
If they just don't have anything useful, and indeed some have nothing useful, well, I always need haulers. (And this doesn't seem to be changing, with the new developments in that field, and that of the mining which means the 'spoil' doesn't accumulate so much.) The big decision is often whether I make so many stone haulers, food haulers, etc, and how many I keep general.
Oh, abut if they have any military capability (even if only dodging), I'll recruit them. Those with family ties into a militia-like unit, who are the last-gasp-we're-all-going-to-die-anyway force, and they're just on a 'refresher' regime, really. The rest are on full-train if they've got no useful civvie skills, and part-and-part duties (scheduled for job-sharing, perhaps) if they've got a use outside of "full metal liaison to the goblin advanced guard".
Dwarf Therapist helps manage all of this (save the military units bit). With it I can nickname and adjust immigrant (non-military) job-capabilities even before they arrive on-site, adjusting those that are already there, sorting by job capability, easily removing all hauling from anyone who has 'a proper job' and I usually disable something like corpse hauling or recover wounded as an additional to 'flag' whether I've dealt with them or not. But I've been going without DT for a few forts, and I can do something similar (though more long-winded) just through scanning the units list and interrogating those with grouped skills, and (again) nicknaming with meaningful (to me!) epithets.
(Anyway, as well as hauling, I also tend to make a lot of rock blocks. Always have done, and particular so now... This bubbles a few levels of Masonic skills into the otherwise unoccupied. I'll often have at least one "non-block" mason's workshop (tied to a particular stone-type pile) restricted to be run by my well-skilled guys, and several block-only workshops where the remainder practice the block-making arts... But it's the construction industry that takes up my time. As well as using the hauling masses[2], the constructing masses get very busy. If I don't want the experts joining in, I burrow them to their workshops and food/drink/beds. But then I'm a control freak!!!)
And I just don't like them dying. Which is a character defect. (Unlike the 'control freak!!!' bit which is... perfectly normal for a DF player, I'm told.)
You can do what you like, though!
[1] Frexample, I don't value hunters as much as a lot of people do (I have plenty of domestic herds that are breeding like made, usually).
[2] I might set a stockpile of the appropriate size near the building site, setting for no bins for exact quantities. As the stockpile fills up I start defining the walls, thus reserving that stone, and then I can de-stockpile that tile, if that fits my need for quantity management strategy.