Should I Replace The Lenses In My Glasses?

I recently switched doctors and got a new prescription for my glasses. My current lenses are only a year old and since I primarily wear contacts, I wasn’t planning on updating them. However, I did notice some changes in the prescription that seemed strange so I’m looking for an informed opinion.
Year old:
Right Eye -
Sph: -3.50 Cyl: -1.75 Axis: 180
Left Eye –
Sph: -3.50 Cyl: -4.75 Axis: 005
New:
Right Eye –
Sph: -4.00 Cyl: -1.00 Axis: 180
Left Eye -
Sph: -3.75 Cyl: -4.25 Axis: 005
Now this all looks like voodoo to me, but I’m guessing it means the new Rx corrects somewhat more for myopia, especially in the right eye, and a little less for astigmatism. I frequently experienced severe headaches over the last year when I wore these glasses; however, the contacts the old doc gave me were awful (hence switching doctors). I’m not sure if the prescription for the glasses was off or if the headaches were just from the drastic difference between the Contacts of Doom and the glasses. The new contacts are working out well, so I trust the new doc – I just don’t know how much difference there is between the old Rx and the new one. If it’s significant, I’d consider it worth the money to get new lenses. If not, a penny saved is a penny earned.
Thanks.