I just noticed that the Coalition app gives more space for describing activities compared to the Common app. Do the top 10 colleges in Eng. such as Caltech, which is both on the Common and Coalition app, look favorably to candidates applying via the coalition app? If one can share her/his experience that would be great.
Colleges do not have a preference as to which application you use if they offer both. If you feel like the extra space will help you then by all means use it.
Unless they changed the application this year, the Coalition Application asks applicants to only write a sentence-long description, so keep that in mind. There are also 8 vs. 10 activity spots, which could be a factor if you would like to separate activities (such as volunteering by organization volunteered at.)
More words <> better.
Schools don’t care which one you use, they care about the content. You should be able to concisely and effectively describe activities in the space provided in either application.