Same Size for Both Lips During Augmentation?

As already correctly noted, the upper lip is generally smaller than the lower.  For purposes of augmentation, this relationship should be preserved.  However, there are anatomic variants and at times, the upper lip may be at least equal in size to the lower.  If the patient so desires, this ratio can be maintained during the procedure.  Generally speaking, making a small upper lip larger than the lower lip is less aesthetically appealing.

In fact, the upper lip should be about 1/2 the size as the lower lips to maintain the correct balance within the face. The puckering that you create with lip augmentation should also be very specific. The upper lip puckering should be in the central 1/4 or about an iris width. The lower lip pucker should be about 3 iris widths. The height of the upper and lower lips should be about 1/2 and 1 iris widths respectively.

Lips need to be balanced. The key is to think about not just the size of the lips, but also their position relative to the rest of the face.
As we age, our upper lips get longer in addition to thinner. You need to think about this as getting the upper teeth to show a bit either with a lip lift or with a filler can help you get the results you really want.
It can also be a good idea to bring in a picture of lips you find attractive. While you can't necessarily get that look exactly, your facial plastic surgeon can speak with you about the characteristics you like and work with you towards an excellent outcome.