You CHOOSE to spend your full second in your WS set by not manually having a macro or bind that has your aftercast(s) in it that you can press directly after your midcast.
Setting aside /equip hands "carmine Fin. Gauntlets +1" etc, because that's not practical for full sets of gear...
You cannot equip two equipsets without a 1 second gap between them, period. It doesn't matter how many packets the game can or cannot receive, your lag, or how many buttons you press/macros you have.
If you have a macro /equipset 24, and another macro /ws "Savage Blade" -> /equipset 25, and you press the first one then immediately press the second one, you will get an error and stay in equipset 24.
If you have a macro /equipset 24, a macro with /ws "savage blade" <t>, and a third macro /equipset 25, and you press the three of them in a row, without a second between the first and third macros, you will get an error and stay in equipset 24.
You cannot, in any way that I'm aware of, equip 2 equipsets without waiting a second between them.
This affects all the things I said above.
-When making macros, all actions that involve an equipset must be at least 1 second apart from each other
-When hitting macros, if you just finished a previous macro, you must (in your head) wait 1 second after the last /equipset in THAT macro finished to hit another macro (if the new one opens with an /equipset)
-If there are actions which take place in < 1 second, you can't do an equip BEFORE and AFTER that action. This is snapshot/rapid shot, like my example, but also FC sets for things like Dia, Flash, and loads of other quick casting spells like BLU spells and certain BRD songs
-You will ALWAYS be sitting in any equipset you use in combat for at least 1 second. There's literally no way to equip another equipset faster than that. You can put on individual pieces if you want, like /equipset 25 -> /equip body "Mousai Manteel +1", but you cannot change your entire set of 16 pieces of gear more than once/second
I'd love for someone to tell me I'm wrong here but I'm extremely confident that all of the above is true.
I don't know how long it takes for GS to change gear, but I've watched plenty of people's streams and videos with equipviewer on so I'm confident in saying it's < 1 second per set. In addition to that, even if it is > 1 second, because of lag or packets or whatever, you aren't punished (being in the wrong set) if you hit the macro too fast or too slow. You don't have to WAIT for your equipset to finish equipping before you can do anything else. If you hit the wrong macro, say you're trying to hit Cure IV but you hit SB (and don't have enough TP) then your character will be doing /equipset 25 /ws "Savage Blade" <wait 1> /equipset 33. You can't just slam your cure macro because if you do, your FC/cure potency equipsets will error out. You can time it between the two but it's pretty tricky and TBH you're most likely to *** up the timing so it's probably best to wait. If you hit a WS but don't have enough TP, same thing...you have to wait the 2 seconds for your macro to finish failing before you can try again, otherwise when you hit it again, you'll get an error and WS in your TP set. This is not true for GS users.
If you have short spells you can make macros like:
/equipset FC <wait 1>
/ma "Carnage Elegy" <t>
/equipset macc <wait 2>
/equipset engaged
But then you introduce a second delay before the action begins, meaning you're slower than a GS user.
You can also use a half-FC set or only equip a few pieces of FC gear...there are some workarounds but none of them are as good as GS, all have at least one sacrifice, some have many, and again...after that elegy is finished, you have to wait a second before doing any macro that has /equipset as the first action, or you will error out and not equip your set.
This is also true for things like DRG jumps and DNC steps. If you want to do one before you do a WS, which is fairly common, you either have to wait a second, use a set that involves 5(6 if you do multiple macros) or fewer pieces, or you can't use a specific set for that action. In all cases,
you need to personally time the actions so that they take place with 1s between them (unless you make Box step -> wait 1 -> WS macros for every WS you could conceivably want to do this for).
I was not aware that you can equip sets from the menu so I would soften my criticism of controller play, though it's still extremely clunky, I guess it is technically possible? Still seems like a disadvantage to me though, especially considering the "space, up, enter" advantage KB has. I'll admit it's not as big of an advantage as I originally thought, though still think it's an easy point for KB.