Not harder, just a bit more fiddly.
From Costar you have only the centre stem fixed to the switch, with Cherry all three stems have to be removed at once.
But, having removed the keycap, with Costar you then have to extract the stabiliser thingies from under the keycap, whereas with Cherry you do not.
Installation is the reversal of removal process, with the fiddly bit of Costar having to hook the ends of the stabiliser bar through the clips under the keycap.