IMOO, this is a question of contrast. The prints from Sunrise are, in general, lower contrast than those from Fotomax. Normally when we look at a small print like 4R, the sharpness plays a more important role. But for 12R or even 18R, the details will become more visible.
Look at the 2 pictures from
http://www.nadir.it/ob-fot_piccolo/contax_eyes.htm. See which one you like better. Also imagine which one is better if they are enlarged.
I have tried to print 4R for the same negative from Sunrise and Fotomax. At first, I thought the one from Fotomax was better. But after a closer look, I found the hair shown from Fotomax was all black while the one from Sunrise still retained some layers.
So my advise is:
If you are going to show the pictures to your father and mother, get it printed from Fotomax.
If the pictures are for your own interest only, print from Sunrise, look for the best one, use the coupon to blow up a 18R and throw all the 4R at the bottom of your drawer.