I was just reading a thread started by a concerned student applying to a college using the Coalition App. Why would a school use that rather than the Common App, please?
You only need to use it if you are applying to a school that is Coalition exclusive, like University of Washington.
Coalition is unique in that they are recruiting students starting in 9th grade which may be a plus (if you think underprivileged students don’t think about their future early enough) or a minus (if you come from a community where college ambitions cause too much pressure already).
SO, @AroundHere , if someone wants to apply to several colleges including U of Wash, but also Common App ones, that poor kid has to fill out two whole applications (besides supplemental essays)? Or can every thing be done at once, funneled via Naviance? Because if the former, geez. How annoying for these poor seniors.
Yes. And even more of a chore is the different word count for the essays. Now, forcing students to edit their one essay or write a completely different one. There should be more cohesiveness between the two apps as to not create additional work for these seniors needing to use both.
This year my kid has three different application systems for a list of five schools, plus additional applications for honors and scholarship programs.
Do not underestimate how much work it is to apply to college.
Most of these are busy work, not useful work. Like filling out your classes, grades, ECs, honors, etc. I thought the goal of Common App is to save student’s time and do these busy work only once. Then you have these public schools such as UW, UC, CSU, Texas, etc., using their own app system and causing people to duplicate their work. The only benefit: you can go beyond the 20 school limit of Common Apps. 
I agree. My S ended up having to use 3 different systems: Common App, Coalition and then, Virginia Tech’s own web portal. The essay will have to be modified for Coalition as well because it comes with a 500 word limit, whereas Common App uses 650 word limit.
Coalition is just clumsy. It is hard to use, and the worst is that you can not preview your application as one complete PDF before you submit.