if len(str(a)) == len(str(r)) and isMult(a, r): faster if isMult is slow?

[maestro]

If isMult is slow then:

if len(str(a)) == len(str(r)) and isMult(a, r):
                trues.append((a, r))

will be much faster than:

if isMult(a, r) and len(str(a)) == len(str(r)):
                trues.append((a, r))

right? seems obvious  but there is no magic going on that wouldn't
make this true right?