I don't know if you already decided or not but here's my two cents...
I have both and I like them both a lot. They are two of my favorite piercings. I find them both attractive and enjoy the vast jewelry selection available. After the initial healing time the lip piercing won't impede your speech much at all. Occasionally I'll bite down in a strange way and catch it making a metallic sound or pulling on my lip but this is rare. A lot of people will tell you that septum piercings are ugly or "cow-like" but I personally find them aesthetically appealing also unlike the lip piercing you can easily flip them up or wear a plug in them to keep them hidden. You don't have that luxury with labrets. I've eaten my fair share of retainers...
As for surface piercings I've had my fair share of experiences with microdermal anchors as well as a surface bar. Both are very pretty and have lots of options for colored or jeweled ends. Sadly though depending on your choice of placement you can end up losing the piercing. Micros though can end up being more "permanent" if they heal as intended. They can be removed it's just not exactly painless. No matter what make sure that you go to a piercer who knows what he/she is doing. There's nothing worse than a poorly done surface piercing...or any piercing for that matter.
Opinions aside though with piercings, tattoos or any other body modification it really does come down to what YOU want. You're the one that is going to have this on her body so you need to decide for you. Good luck and enjoy your new bling!!![]()