version 18 you can keep [apart from the online catalog etc if you have not downloaded it] magix support this, xara do not, the updates are few and far between; magix support is....difficult

version 21 is technically xara pro+ [as opposed to just pro] it is the only program xara now support - you get frequent updates, but you lose it if you stop paying - the two channels, magix and xara run side by side

no-one has yet said what will happen when the magix version reaches version 21, and as is par for the course with xara, there will be yet more totally unneccessary confusion over version names

but that aside, you can get a discount on pro+ which brings it down approx 50%