DirecTV Gemini Air vs. Stream App Downloaded on Samsung Smart TV or Apple TV

I recently switched internet/TV service from Xfinity to AT&T Fiber and DirecTV. I purchased the 1GB internet, and my TV is connected via wifi. I downloaded the DirecTV app to my AppleTV, but the sales person also signed me up for the Gemini Air which I haven't installed yet because the technician who actually installed my internet service said I didn't really need the Gemini Air device since I have a smart TV. And so far I've been able to access DirecTV by just using the app.

Does anyone have any insights on whether it's generally a more stable connection to stream DirecTV content via the app on my smart TV or Apple TV, or is it better to stream using the Gemini Air dongle? Stability of connection, video/sound quality, etc. Interested to hear if anyone else has experience using both and what they feel is the better way to go. Thanks!