Which one would you pick considering the new price of the Ghost (269EUR + 49EUR for a tophat)
It depends.
There are many factors involving the choice, like cooling limitations or components person wants to use etc things to achieve. From my experience Ghost S1 is way easier to build in and is better quality, better panels, but has limited features. One can't mount many fans or big coolers in there, and you've to rely on top hats. Though case looks absolutely stunning, there are some issuues with quality sometimes. Though i am not a big fan of top hats as they don't look nice to me , but it's up to the person.
Meanwhile Ncase... Well the paint on the chassis , inner, is very thin so any screws scratch it easily..it kinda ruined aesthetic of the case for me, washers might solve it or screws need to be tightned carefully, - that was a slight minus for me. Then I had problems with Motherboards aio shield, that thingy on the back, for some reason my motherboard didn't push it back enough so it always use to fall back and leave gaps...it felt like mobo was too far so it couldn't push it back into the slot, might been just me. Aside that i've not experienced any issues, well the only one is that as the case has more room for fans to install there's a difficulty setting them all and connecting all those cables nicely, but it depends on the user and how he prefers his build to be, it's not mandatory to fill every slot with a fan. Case itself has room for SSD 2.5 or bigger psu's, or bigger heatsinks, slot for AIO is in better position too if compared to Ghost s1 which requires a large top hat.
So looks aside or size, Ncase is superior in it's layout and features.
Well and getting Ncase is easier as once it's available on site you can order it, track it, and get within a few weeks window. Ghost s1 takes months to arrive sometimes and might cost some nerves.
As I have i9 9900k now i kinda feel that getting Ghost s1 might have been not the best decision or opposite getting that CPU for Ghost haha. Case itself is thick and can get very hot too, a top hat with exhaust fans might be required to push that heat out, so it's not that simple. Unless build is kinda not overkill with high end components. Ncase just handles high end builds a bit better at the cost of size and maybe looks.
It's just my opinion honestly, the same stuff could be said about any case even skyreach or whatever which is even smaller.