Some of these Mark 4S parts will become a Prusa Core One. (Credit: Aurora Tech, YouTube)One of the interesting things about Prusa’s FDM 3D printers is the availability of official upgrade kits, which allow you to combine bits off an older machine with those of the target machine to ideally save some money and not have an old machine gathering dust after the upgrade. While for a bedslinger-to-bedslinger upgrade this can make a lot of sense, the bedslinger to CoreXY Core One upgrade path is a bit more drastic. Recently the [Aurora Tech] channel had a look at which upgrade path makes the most sense, and in which scenario.A big part of the comparison is the time and money spent compared to the print result, as you have effectively four options. Either you stick with the Mark 4S, get the DIY Core One (~8 hours of assembly time), get the preassembled Core One (more $$), or get the upgrade kit (also ~8 hours). There’s also the fifth option of getting the enclosure for the Mark 4S, but it costs about as much as the upgrade kit, so that doesn’t make a lot of logical sense.In terms of print quality, it’s undeniable that the CoreXY motion system provides better results, with less ringing and better quality with tall prints, but unless you’re printing more than basic PLA and PETG, or care a lot about the faster print speeds of the CoreXY machine with large prints, the fully enclosed Core One is a bit overkill and sticking with the bedslinger may be the better choice. The long and short of it is that you have look at each option and consider what works best for your needs and your wallet.