Sorry, should have mentioned that! We have no upper cabinets near the range so it would definitely fit. I don't do much frying, honestly, but I thought for aesthetic purposes alone a 36 might look better...

Our range is a samsung gas range. 18,000-BTU.

How many cfm does the hood move? If you have a high-power hood, you will be able to catch more steam and grease before it spreads.

Sorry, read it wrong. It actually says total power: 57,000 BTU. The hood says 400 CFM

Good news is that you probably won't need make-up air for 400cfms (check with your GC or local safety code). But that's fairly low power (mine is 390cfms), so a larger capture area (wider hood) would be helpful.

If you can remember to start the hood as soon as you turn on the burners, so that you have some suction going before HOGS appear (heat, odors, grease, and steam), you'll probably be OK. My hood is the same width as the range--I didn't replace existing cabinets, and IRL I don't know anyone with a wider hood. In fact every other house I've lived in had a recirculating hood, including my old kitchen. Hope this helps you decide.

ETA, if you post on the appliance forum, I think they can help you figure out how many cfms you need per BTUs, if you need that info.

I do think aesthetically that hoods without surrounding cabinets look better and more proportional when the hood is a bit larger than the range. Depending on how much empty wall space you have, you might even look at 42".

This is a rare case where it'd be more functional AND look better to swap, so it seems an easy decision to do so if you can spare the money.

I'd go with the 36" hood if you can. And make sure you have the right sized ductwork for the larger hood...8", I believe.