The mobile app is specifically for the field worker (admins can log in to the mobile site). For us this is huge b/c with our previous solution there was a single app for field workers and admins, and even though you could control things with roles/rights, both workers and admins saw essentially the same interface. Less than ideal. We want our field workers focused and need the app to be super simple for them to quickly and easily use to get the job done.
Integration: perhaps the biggest things for us. Nearly all similar solutions had zero or nearly no integration beyond accounting (Quickbooks, etc) and payments (Stripe, etc). Call of Service has those and also Zapier integration, which of course opens it up to hundreds of integrations. While the Zapier integration is very basic at the moment they are actively building it out and we've been assured that a robust offering is around the corner.
Support: so far has been fantastic. Very fast, helpful support. They seem to genuinely care