I just tried it with Subs

Form version, 1,000,000 calls = 0.45 sec
Module version, 1,000,000 calls = 0.26 sec

The sub was very simple, dim an Integer and add 1 to it.

PLUS, for interest

When I add a doevents into the loop after the sub, not in it)

Form version, 1,000,000 calls = 9.65 sec
Module version, 1,000,000 calls = 9.01 sec

(All data averaged from three tries)

in general, modules look quicker by about 0.2 - 0.5 sec per million calls,

or 0.0000002 - 0.0000005 sec per call

you wouldn't normally notice, unless you were looping the call millions of times.

This also gives you an idea how how much inline functions would increase performance (if they existed)