This thread might help: Browserstack Vs Saucelabs Vs Crossbrowsertesting.com - #2 by ychaudhari
I don’t use any but Sauce Labs recently merged with API Fortress, so you could run your API tests in there also. Which would be nice to have all your tests orchestrated in 1 area.
I think most vendors are offering all the same anyways, you are going to have to look at why they are unique and what else that they offer in services.