Completely normal to have one a little bigger than the other.. Only worth doing surgery if you are in pain or suffering severe distress to be honest - NHS won't fund it unless there's a pretty big reason.
Having had a labiaplasty (mine were touched my thighs if stretched and caused endless problems and infections) I really would try to live with it unless it's very sore. The operation I had was hell on earth and I wouldn't say to anyone to put themselves through it unless you really feel you have to, I spent the best part of a week pretty much bedridden - although mine was quite an extensive op, had the clitoral hood and labia minora drastically reduced.
It is obviously bearable if you are in severe pain a lot of the time, if it's really affecting your life then do pursue surgery. Sometimes they will expect you to try other treatments first (if going with NHS), my problem was identified not long after birth - my mum told the health visitor I wasn't normal there from her (limited) experience, GP said it was called elongation and needed an op when I was age 3, wasn't accepted for surgery until I was 20, after going back and forth to gynae regularly and trying various creams and that, but generally if you get a good referall and can demonstrate how much it bothers you, you might be able to get an op..
Pyschologically and aesthetically though, there's no reason to have it done. Our vulvas are unique, they aren't meant to be symmetrical and aren't meant to be pretty either.. It's not too too rare, I think a lot of women have similar issues, my GP said mine was quite bad but that she had seen worse, my first gynaecologist said it wasn't an unusual problem either.. We tend to think it's rare though as like you say, we never see people's vulvas but it really does seem to be something a lot of girls are affected with..
Possibly worth warning you as well that any surgery will leave scars - I have an obvious line where I was cut, so surgery may only cause more "aesthetic" issues. Not to mention the fact it can cause pain as well, long term - my scar's still a bit tender especially at the ends where they just wheeked about 2cm off :O
Hope I haven't been too graphic - honestly, if you do feel you need surgery I can offer you coping tips for the pain, just pm :) - but you really are best living with it, if you feel you can :)