Hmmm, this thread took an interesting turn.
I find that the slim browser is quite efficient in systems with minimal resource machines; but since it is a Chromium engine, I do prefer Firefox. As the slim browser is designed to work with minimal resources I find it difficult tho believe that it doubles as a snooping agent.
Google is not my favorite organization for a variety of reasons and Google does have a history of 'obtaining' information regarding users web travel. I do not go out of my way to avoid their products or services, I just have preferred products and services.
In any case, if you are that concerned, you could always use a packet capturing tool to monitor your network traffic while the browser is open (Wireshark, among others provide excellent capturing/filtering options), and/or control (and monitor) your cookies.