Actually I think it is IFR flight plans that benefit more from online filing.
That's because a VFR flight plan cannot (in modern Europe) be refused. Nobody checks the route for validity, for CAS infringement, whatever. You could file a VFR FP right across the UK at FL100.
But an IFR one can be refused for various reasons, which is why a rapid online facility is very desirable, so you can tell right away if there is a problem.
And an online facility is handy anyway because you can get the notams (for which internet is mandatory anyway) and file the flight plan in one session.