I would never take either Actos or Avandia they are very unsafe meds & in fact have warnings on them. Metformin is one of the oldest, safest, cheapest drugs & has many other advantages: helping hearts, cancer & building beta cells. 500 mg is the smallest dose possible & is usually rx'd only as a starter dose. You usually start increasing the dose as you get used to the drug. I take 1000 mg twice a day.
Taking your medicine like actos or Metformin TR when having diabetes will depend on your body reaction. It doesn't base for the quality of drug coz other people are well happy with actos while others doesn't.
I WOULD OFFER THE FOLLOWING:
Metformin in sufficient dose cuts back liver glucose release.
Actos forces more glucose into body skeletal muscles when they are even full of glucose. It seems the water retention is greater under actos.
For me I had to give up actos as my kidneys starting to go down hill and dropping efficiency with protein in urine.
That has stopped once off of actos and a1c sub 7.0.
Be careful about actos. kissing cousin to avandia.