A lot of times I like to compare the only two recurring girls on the show: PIXAL and Nya. So I guess I'll just let you look inside my brain a little and see the points I usually touch when comparing these two women.
First of All: Why even have girls?
This is obviously a show aimed majorly at boys. So why have girls? Well, I think there are two different reasons.
1# To be politically correct
This generation is really focused on girl power. If the show was all about boys, some people wouldn't consider it politically correct. So they had to add a girl character (Nya) to inject some strong women power into it.
2# To give the male characters more depth
What would Jay be without Nya? What would Zane be without Pixal? And these male characters are broken-hearted when their significant other is missing. If you haven't noticed, Zane really really really cares about Pixal. And this gives him more depth as a character. Kai really really really loves Nya, and it gives Kai the big brother vibe that he wouldn't be the same without.
Now to compare the two:
Both Nya and Pixal have a little bit of sass. I find Pixal's sass a little more appealing than Nya's. Nya just seems rude sometimes. And Pixal does have that innocent vibe to her that Nya doesn't have.
Both Pixal and Nya are both smart. They always seem to be the one behind the computer, building mech, saving the ninja... To digress a little bit, I feel like Pixal has taken Nya's place. Pixal is now Samurai X, Pixal is now the one left behind when everyone goes on missions, shes the one building the mechs, she's the one saving the ninja now. She's filling Nya's place since Nya left to become the water ninja. And even though I love Pixal, I think I liked Nya in that role better. Nevertheless, they are both highly intelligent.
Their Development as a Character
Let me say one thing right off the bat. Both Nya and Pixal are underdeveloped. Lego, if you're going to add girls into the mix, at least give them some depth! I notice the underdevelopment the most in Nya because she's kinda moved into the main character role. Nya just, isn't interesting. I can only think of one thing that gave some kind of interest and background to her character and that is the whole thing with their parents that happened in season 7. But since she shares that with her brother and her parents came back, I feel like that's not significant. I could name 5+ things about the other ninja that give them depth but only about 2 for Nya. Pixal doesn't have much depth either, but for some reason, that doesn't bother me as much.
Well, thanks for coming along for the ride! Good evening, fellow fangirls and boys, GOODNIGHT!