Prescription -6.50 but
Q: I have a prescription sphere -6.50 but have glasses sphere -6.00. Will I notice much difference?
If the question is to stay or not with the old -6.00 diopters you have...
Usually, you change your prescription if the old one is no longer good for you and your vision is not the best.
If your old prescription is still satisfactory, your vision is good and you have no additional symptoms (headaches, tearing, dry eyes), there is no need to change it.
Another theory suggests that as a myopic, you should always have the maximum diopters which give you the maximum vision, preventing further increase of diopters in time.
If you tried the -6.50 at the consult and there was no difference, you can stay with the old ones, but if your vision was better, you should change them.
Hope this helps,