If physical laws stayed the same, you would notice a difference indeed.
Scientists have tried to estimate the height of biological beings (so in fact aliens that also walk shouldn't be much larger than we are :) ) http://arxiv.org/abs/0708.0573
I think they don't assume any specific dimension (like radius of earth), but just consider stuff like radiation of heat and breaking when falling.
I didn't go through the details, but in short: yes, you would notice a difference, if only dimensions but not physical forces change.
in Einstein's relativity,
he once thought that everything is relative.
if you were to grow larger, but the world remains the same, so your size increases relative with this world. all measurements are relative.
however, if the world is being enlarged together with you with the same factor, then how do you ever notice any changes?there is nothing that you can compare to, to show that you are increasing in size.
of course the increment is not simply just the increase of spaces between atoms etc, it means everything including the sizes of atoms and mass, so that you will never detect any changes.
so to say that this kind of measurement is meaningless.
that was one of the postulate in Einstein's relativity theory.
and of course the real case might not be the same as above, or if it is, we will never notice too.
and then Einstein showed that the only absolute/ non relative thing in this world is only the speed of light