Planning on purchasing a SS sub date. Need help deciding

[bimmer]

I am planning to get a SS sub date as I really like the look of it but then my concern is: is it better to go with a M serial or earlier series given the price difference?
Other than the chapter king, the bar code, are there any significant differences between the M serial with the earlier ones?
On the other hand, should I hold off and wait for the ceramic bezel sub?