I think I am narrowing down my search - Trek FX 7.3, Giant Rapid 3, Specialized Sirrus Sport, Cannondale Quick 4. Comparing online specs the Giant is different than the other three in the gear ratios:

Group of three: 48/38/28 and 11/32
Giant: 52/42/30 and 11/28

Is this enough of a difference to be noticeable?

Background: Just getting started, rides will be 10-30 miles, mainly excellent fairly flat paths. Intending this as a more comfortable first road bike.

All of those bikes have pointlessly high gearing for anything other than maximizing speed on a downhill. (Assuming correct pedalling technique - which means a good rate of "spin".) But there's no harm to it - with modern gearing systems you have a very wide range of gears, so it's ok to waste some. So just strike this factor from your decision.

The gears on the Giant are exactly my gears and I love 'em.
They are a bit higher than the other's, which are typical touring gears.
The touring gearshave a lowest of 28/32 to go up extremely steep hills (20% and more) ... but if you are fit enough you should be able to do everything on that lowest gear of 30/28.
The 11/28 of the Giant has a smaller gear difference and thus has more usable gears, making it better.
If you are not doing any offroad with steep hills, you might even want to change that cassette to a 11/23, I've got one on my racewheelset and love it

You're just getting started with biking? Then I would opt for the lower gearing. Go with the 48/38/28 and the 11-32 cassette on the back. You'll have an easier time on the hills.

The difference may not seem like much when you look at just the rings in the front. But factor in the rear cassette, and you'll notice the difference.

The Giant is geared higher than the other bikes. The difference would be noticable on steep climbs.

Do you currently have a bike? If so,you can plug your specs and the specs of the bikes you're looking at into Sheldon Brown's calculator and see the differences.
https://www.sheldonbrown.com/gears

drop 'em and get a compact crankset.