I'm trying to understand what they're proposing for my renovation. The guy at the store says it's basically the same thing but with different names, and I'm completely lost. Is it really the same thing or are there differences I should know about before investing?
It's the same technology, so the guy at the store isn't wrong - but it's a bit more nuanced than that. An air-to-air heat pump is the technical name for the system. A "reversible air conditioner" is just another name for the same thing, used mainly to say that it can do cooling in summer AND heating in winter (reversible = it can work both ways). So yeah, it's the same thing in the end, just different terms depending on who's talking about it.
The real difference to check isn't in the name but in the model they're offering you. There are basic air-to-air heat pumps that do just the minimum, and others that are way more efficient at heating in winter (better coefficient of performance), with better sound insulation, humidity management, etc. Some work better when it's super cold. That's where you really need to dig - ask the salesperson for the exact specs, the heating COP, whether it'll work well in your climate, and check reviews. Don't stress if you use one term instead of the other, people understand it the same way everywhere, but don't let yourself get sold just any model just because it has a nice name.
The real thing to remember: an air-to-air heat pump is the complete system that pulls energy from outside to heat or cool your space.
A reversible air conditioner is just the same system but marketed differently, with emphasis on the "reversible" part (= capable of heating AND cooling). Technically they're identical, so the guy at the store is right, but watch out that he doesn't push some crappy brand on you just because it's cheaper - I've seen people have a rough time with units that start acting up after two years.
Really look into the brand's reliability and the mandatory annual maintenance before you sign anything.
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