Is there a standard measure?

Not that I am aware of. The only tool maker that routinely seems to
publish input and output figures right across the range is DeWalt. Vis:

http://www.dewalt.co.uk/powertools/p...catno/D21721K/

(On the battery stuff they publish only output power)

Presumably they're using a dyno to measure the actual power available
at the tool mounting?

Even that won't be the whole story - what we really want to know is
how well it saws/drills (in our hands, not someone else's) - which
will depend on the quality/concentricity/flexing of the tool (and our
personal skills/style etc) - and in real world conditions.

Best test is still borrow a mates and use it for a hundred cuts/holes
with it.

When it comes to pro tools, they're virtually identical in features
and specs at a particular price point anyway.