Colchester Chipmaster....
....but then I have 3-phase, lots of space, and a hankering after big toys.
I could be wrong, but IIRC the Chipmaster is at least twice the size of the Myford...
Then you've got to take into account the wear: Which machine's done the most work, and is the most worn? What about tooling? The one with the most tooling for the money is probably a no-brainer...
But, ultimately, it has to be your call.
www.lathes.co.uk is an excellent site to begin your research on; look for the lathe with the fewest drawbacks & the best set of features that you'll use - and buy that one. Don't forget to take into account transport costs; a Chipmaster is going to cost a LOT more than a Myford to move around... it weighs over 1/2 tonne before you add tooling...