First off I do believe this in no way compares to the argument of balancer vs. a nail,
as for how much better one is over the other I could not tell you exact, but that
there is a difference between the methods and the machines is for sure.
A regular grinder takes longer, as for the angle...
Granted, a dedicated blade grinder has the angle pre-set, but the wheel itself
wears and as it does the angle changes, requiring a physical adjustment.
There is no warning the wheel or the machine gives to indicate out-of-angle adjustment requirements,
there isn't even a pre-defined number of hours or sharpenings that after every so many you do it,
instead the adjustment is performed when the operator feels that it needs it, and it is thus a matter of
estimated guesswork at best.
Further, this adjustment in no way guarantees the angle per se, unless it is done
with a measuring instrument which I have not seen on a blade grinder.
The angle is supposed to be correct once the wheel is adjusted to certain specs,
but as wear and tear makes the wheel smaller, who knows for sure?
To me the argument that a blade grinder gives a better angle is moot, it should,
but it all depends how often it is re-set, and just how accurately the re-set is.
That it is more consistent, yes.
And that it sharpens blades faster, more evenly, and the blades suffer less from heat degradation, absolutely.
It is definitely the professional way, also it considerably reduces time spent on this part of maintenance,
hours turn to minutes with a machine that can sharpen a blade every 15-20-30 seconds.
Maybe not quite, but I usually sharpen my 30-odd blades in about 20 minutes.
As for whether it's worth it, I think only you can know that answer.