The Thameslink route where they work now is being upgraded and needs stock with metro-style interiors, automatic train operation and higher performance to run the very intensive service across central London.
The only other place suggested for them is the GW suburban lines but the view here seems to be that a higher performance unit is required as a lot of the running will be on the fast lines.
These issues are less of a problem on the lines north and west of Manchester where they will definitely improve on the Pacers and Sprinters in terms of performance.
I think most would accept that the 319's are a small step up. I am even prepared to accept that there may be a case for replacing the 319's on Thameslink (although the comment re Metro interiors might be disputed by the longer distance commuters, and I cdont understand why they cant be retrofitted with ATO and the traction eqpt upgraded. Surely cheaper than new trains.)
What seems to be annoying most up here is that "the south" always seems to get new EMU's whilst " the north" has to make do (most of the time) with the south's leavings. If we're having a newly electrified line why cant we have new stock-"the south" would get new stock in these circumstances? Why cant the North West have new Electrostars and Southern keep the 319's for some of its other services? Or let Boris use them on his services rather than new all the time.
Nobody is really giving a sensible justification for what is proposed. The arguments are around-
"we should have better in the south because we pay more tax" which is debateable.
" we earn more down South so we deserve better" again which may be debateable but is certainly no justification (why should a bank clerk in London travel in better trains than a clerk doing an identical job for the same bank in Manchester purely because the former receives London allowance in his pay?).
" the TOC's down South receive less subsidy so can afford better trains". What cash goes in/out of the TOC's is effectively a Government decision who have also decreed the services to run. So why should our Manchester bank clerk suffer because his TOC's subsidy level reflects having to run some basket case services (eg Settle-Carlisle) at Government request. Manchester-Liverpool may be profitable for all we know.