very different, because they aren’t (typically) wired in the same way.

what gives (typical) humbuckers their sound is two coils being wired in series. on the other hand positions 2 and 4 in strats get their sound from the two coils being wired in parallel.

if you have a chance try a HSS guitar with coil splitting in position 2. i think most have it these days. that will give you

position 1: full bridge humbucker (series)

position 2: split-humbucker bridge + middle pickup in parallel

A/B those switch positions and you will understand the difference very quickly.

Can confirm what the other poster said, very different. In addition, a humbucker with a coil split doesn't really sound like a single coil generally (there are some things you can do to get closer, but we're only talking about raw pickups with no mods here).

It all has to do with the windings and the fact that the magnets aren't interacting the same way. A fender Texas Special bridge single coil is about 6.56k ohms impedance. The Shawbucker 2 is about 7.8k ohms. So humbuckers today aren't really just two single coils flipped and stacked. I don't know enough of my history to say whether that's how they started, but if someone were to claim that I would totally believe it.

In my experience I’d say they’re very different. I have an SSH and SSS strat and bridge+middle with single coils is not going to get you in the realm of a humbucker other than the noise cancelling aspect.