Have you sat in a GLA? I’m not sure why they call it an SUV; it’s more like a little station wagon. Certainly not a vehicle you would take anywhere off road. MB makes legitimate SUVs but the GLA is not one of them. 
Glad to hear you are happy with your Mazda.
I haven't sat in one. I've seen them up close at grocery store parking lot. They look to be the same size as the CX3. Although I have AWD, I wouldn't drive off road. The GLC has a similar body style, but is larger.