If you go back far enough, the East Coast stole a march on the West Coast when BR IC decided to divert the daytime Inverness service to run from King's Cross with a 125mph HST.
The 110mph West Coast could not match that, and also the direct route avoiding Glasgow (via Coatbridge/Cumbernauld) was downgraded with through trains diverted via Edinburgh (reverse).
So what was once a historic WCML/LMS route transferred to the ECML.
Going the other way, the East Coast sleepers to Aberdeen/Fort William were transferred to Euston along with the Inverness service, but via Edinburgh.
BR XC continued to run through to Dundee/Aberdeen on the WCML via Edinburgh.
Post-privatisation, the WCML (VXC) ran to Dundee and Aberdeen, but were cut back to Glasgow/Edinburgh under AXC/TPE, with through AXC services via York (ECML), despite the slower route from Birmingham.
Pendolinos were due to reach Stirling under Virgin after electrification but never started.
Avanti now has bi-modes which could (if DfT so wished) run into central/northern Scotland via the WCML and Edinburgh or direct, but have clearly decided to concentrate on services south of Preston with these non-tilting bi-modes.
The HS2 plan has yet to work itself out, but it did promise Euston-Glasgow/Edinburgh services, splitting at Carlisle.
But the demise of the Golborne link means this is unlikely to happen.
Both routes have their strengths and weaknesses, but it does seem the ECML has the edge at the moment.