Is Glycomet 250 Or Glycomet 500 SR Better For Slightly Elevated Blood Sugar Levels?

Hi Sir, My mother is diabetic from last 5 months, her diabetic level is 165before food and 275 after food. As if now she Is taking glycomet 250 twice a day. Diabetic level was not decreasing so Glycomet 500 SR for twice a day has been prescribed by another doctor. Pls guide me which is better.