Existing through wall AC or split system

I have no idea if you'll get it back in terms of resale value (probably not, but I expect that's the case for much of your renovation anyway).

Having lived with both split system + through the wall setups though, the split system setup is a *lot* better if you can do it, mainly because it is far quieter (makes a big difference if you're trying to work or sleep), and also gives more even cooling if you can get more than one fancoil unit in your apartment, in a central location - through-the-wall is obviously always going to be one big unit one one edge of your apartment.

Not sure where you're located, but one big issue with the split systems is the placement of the condenser unit. Some buildings have restrictions on where they can be placed, and the NYC zoning regulations also restrict their location.

I think what is important is deciding what a likely buyer would do if they purchase the apartment. If it is likely they would need a split system than you might get your money back plus maybe a little more. Same with kitchen and bath renovations. I try to make most of my renovation decisions based on what a likely buyer would want AND be willing to pay up for. Lots of buyers do not want the headache and prefer an apartment in mostly or completely move-in condition. Such apartments will get a price premium.

Split units hands down or Central ac if you are redoing walls anyway.

i added central AC to my new apartment as part of a gut reno and like it so much better than the PTAC units that my old building had. but it's a much more involved job than through-wall, including lots of patching and repairing of interior walls. also had to go through a mini nightmare with DOB requiring us to demonstrate compliance with city noise codes. in the end, it was worth it.

Some of it depends on how long you intend to hold the unit and the (unknowable) future tastes of the market. If during the time you own the place the market comes to expect split/central AC as a litmus test of whether or not a unit "needs" to be renovated, the discount you have have to take for NOT having it could be a lot more than $25K.

> also had to go through a mini nightmare with DOB requiring us to
> demonstrate compliance with city noise codes

I don't understand why the city makes it so hard for apartments to get central/split air conditioning units. Window units are louder, drip and sometimes fall on people, but anyone can install them. Not to mention all the zoning roadblocks that you hit when trying to install into a multiple dwelling building.