It's a native app that I have control over and doesn't suffer from browser incompatibilites. Doesn't "feel" like a webpage riding on HTML. Nothing beats local horsepower. GMAIL is for the average weenie with shallow pockets and/or no need for real functionality and are naive with their reliance on the privacy giants of the day. Nuff said.
It has much more capabilities and serves as a one stop organizational shop...it's technological capabilites far exceed that of a FREE client such as GMail.