Rail-wise, poor Plymouth comes out way behind Exeter:
the whole hour it takes to go from Exeter means Plymouth is remote in rail terms from London.
there is no real "metro" system ^ la Exeter.
whereas Exeter has two direct lines to the capital across southern England, Plymouth has just the one.
Not sure if a metro service running from Friary via Laira to North Road has ever been mooted. Also, a line from North Road via Tavistock Junction, up the Plym Valley line and then a new short spur across to the Derriford/Airport area seems possible. In both cases, services could be extended to Gunnislake/Tavistock.
Which is why Air Southwest now fly Plymouth/Gatwick 4 times a day and Plymouth/London city airport twice a day.As I heard a gentleman from the Plymouth business community say on radio Devon in response to calls by the Green Party at Glastonbury recently to curb airport expansion "It is not feasable at present to conduct business adequately on distances over 200/250 miles now other than by air"Rail Journey times of 3 to 3 1/2hours from Plymouth to Paddington are simply no longer good enough in the 21st century when there are now faster and sometimes cheaper alternatives hence the reference no doubt to "Poor transport 'is holding city back".