Hi
Its your decision, look at each lathe with the the myford ml8 you will have a better speed range the coronet there are different speed ranges depending on when it was made and what model it is ie a major ? a majorette ? a minor ? Or a. minorette all this boils down to the attacments that you have with yours.
There should be a little brass plate just under the bed bars that will tell you which model you have , then its down to the attachments you have if any?
This boils down to two points ie the bearings on the myford are steel roller or ball bearing over for the coronet lathe which has a phospher bronze bearing which is a pain in the arse not to replace but which kind.they come in at about sixty quid inc vat.
Next chucks i have never seen a coronet with a chuck on the spindle but that could be me and my ignorance
The coronet has a spindle nose thread of . 875 x18 tpi
The only people who make a insert for that thread dimensions are robert sorby if you do go with the coronet the loading of the chuck plus a blank and cutting forces the bearing will not last long.
I would not choose either because like all things progress has made its self felt even in woodturning
But i understand the economic argument and peoples personal financial situations.
Good luck with you choice have look on u tube for both machined.