You can pry my 1" threaded headsets and quill stems from my cold, dead hands.

* Better looking
* Easier to adjust stem height to suit rider position, especially on the road
* Greater range of adjustment
* Your fork and front wheel won't end up on the floor when you pull the stem out

Threadless steering system components only came about to save bicycle manufacturers money and to simplify their supply chain, with manufacturers saying "they're better" without any real data to back that up. And, because it was "newer, and therefore must be better", cyclists took the bait hook, line, and sinker. True, in the longer run, it allowed for things that could never happen with a threaded steerer, like carbon steerer tubes, but 99% of the population really doesn't need that.

/grumpy old man

Pete

Stick with threaded. Just my opinion. Your LBS just wants to make money, avoid hassle, and get you out the door.
There are tons of stems that would look just great, and you really only have to "undo" one side of the bar to swap stems.

I'd find a different LBS. It's not their bike, it's yours.

I'd go for the new quill stem too.
If a fork change were absolutely necessary, only then would I upgrade to threadless. Which is what I did.
But not if the bike were actually C or V.
A 25.4 mmØ steerer tube can be made to be stronger, stiffer, and lighter than a 22.2mmØ stem quill, regardless of material.

25.4 is threadless, correct? And by stronger, stiffer and lighter, do you mean significantly? As is, my front end is stiff -- I can't flex it no matter how hard on it I am.

Yes, and somewhat.
But it sounds like you should be fine with the threaded.
Make sure the replacement stem is of at least equal quality.

Hopefully,it will be. I plan to install a titanium quill stem to keep with the titanium theme of the bike.

Sweet Looking upgrade! the schwinn.