Hi guys. I'm fairly new around here and like to keep my nose out of a lot of things going around like this, but I feel fairly confident I know the answer, or answer(s) for that matter.
1. Miranda Cosgrove has been with Nickelodeon for a much longer time.
2.In general, Miranda has been acting longer than Jennette.
3. iCarly is Miranda's show, if Jennette had her own show and Miranda was just her co-star she would be making more than Miranda.
4. She has done more work for Nickelodeon. She sponsers them, rakes in at least thousands from her albums, played in more movies for Nickelodeon (School of Rock, Drake and Josh movies,...etc.)
5. Jennette is just now starting to branch out from Nickelodeon doing other things, while Miranda has done other works from there, meaning Nick may have been afraid they'd lose Miranda to another show or channel.
6. It may be slight favoritism in Nickelodeons part (also Dan's), but they feel Miranda Does more.
Ok, now that i have said that, I just wanna clear things up. I LOVE Jennette and her acting and i know she's played in nick movies to, so at least they liked her enough to star in her own movies or have a main role. I don't even believe Nathan Kress gets that, so feel something for him. I think Jennette gets more than Nathan so be happy in that way. I love all the actors on Nick for the most part, but Nick is guilty with every show, not just iCarly, with favoring the main stars. Also, dan may treat them better, but only because they have worked for him before, so maybe he just gets along better because of their start on Nick. This is just my opinion, every fact i've stated though is true, just in the form of my opinions. Thanks for reading.