Have been testing the Google Home app on iphone to control Smartthings. What i have found, to my surprise, is it is faster to control your ST hub than the ST app.
GH does not loose the connection to the hub like ST APP
It shows status of things immediatly, while the ST app does not. ST loads, hesitates and then says downloading before giving you control.
If you turn off a light in GH the light turns off instantly. ST takes a fraction of second longer.
GH gives you control over dimming and color temperature on IKEA bulbs on the same window. ST does not. You dont actually have do anything for GH to offer dimming as they group all lights in each room - convenient.
GH is not without flaws, but as a tool for regular family members to control a house it is far better.