I know when you look at it you see one side weaker than the other but you are probably the only one. I think most guys have a side that doesn't fill in as much or look as good in the earlier stages. I know I do and it seems to be very common. Just stop comparing them in the mirror and just go with your overall look when you glance in the mirror. No one is looking at both sides of your face at the same time anyhow. I'm months into a full natural beard now and I'll probably have to go back and look at old pics to tell you which side was my weak one, just give it time and it will either catch up or you can trim to sort it out once you see what it's doing... just try and give it months and not weeks. I think your beard is looking good and you should keep it growing!