How did you choose your main's race, and why do you stick with it?

[Atoli]

How do you stick with it when you see chars of other races looking super awesome?

That's easy - I don't
There is this wonderful thing called Fantasia, and..yes..it easily gets you addicted, but that's okay °-°
It's okay, you hear?! Take it! Drink it! Again! You will like it and you will understand me!!

Okay, on a more serious note x)
I was Miqo'te for the longest time. Emotes are usually the biggest deal for me, because something that feels super natural to you might be incredibly awkward on a different race.
Miqo'te emotes just felt right for me. Also, they were nice and girly but still had something that made them more "exciting" than boring normal humans (cat eyes, fangs, ears and tail).
I had decided I'd switch to Au Ra once HW would be released months in advance. But it still took me nearly a full year and lots of Fantasias (going back and forth between Miqo'te and Au Ra..and Lala because why the hell not) until I made the final decision and also changed my name to fit the new race. That helped settle down in one race, because having a race-specific name would be weird as the wrong race

Au Ra are fairly common as well, but honestly, I wouldn't mind that if I were you. You pick it because you like it. What's the point in playing a race that is rare if the reason that it is rare is because most people think they look ugly?
For example, there are usually only a handful of female Roegadyns on each server. If you just care about rare, that's the way to go. But there IS a reason they are so rare. It's very hard to make them look good (and even then, it's really a matter of taste).
Miqo'te and Au Ra are popular because they fit the common ideal of attractiveness, and I don't see anything wrong with following that if that also fits your own ideals best

@choosing:
I originally chose Miqo'te because I love cats in RL and I had only played MMOs with normal humans before, so it was pretty cool to be able to play as a race that looked and moved so much like my favorite animal.
The distant, otherworldly beauty of the Au Ra ladies captivated me through the trailers and benchmarks though, and once I had a taste of it, going back to Miqo'te felt..boring, too familiar, too in-your-face.
So I ended up going back to and sticking with Au Ra, even though I sometimes miss the direct, earnest emotes and natural way of moving that the Miqo'te had

But I'll be honest: I WILL get the cravings to be a super adorable lala again, or a fluffy kitty, so I'll end up throwing money at SE again for more Fantasias. It's just that Au Ra is my MAIN race now, the one I go back to after all the raceswitching craziness ^^°