We've had a 2018 Terrain and a 2019 Acadia and have been much happier with the Acadia. I know many people complained when they downsized, but for our situation, the size is perfect. We've have been very satisfied with the MPG for that size of vehicle.
Since the '19 Acadia still has the older infotainment system, ours has the audio text message via Bluetooth feature, which is convenient. Although, I usually long press the steering wheel button to trigger Google Assistant on my phone for sending texts. Android Auto does work well, but for short trips I don't bother plugging the phone in usually.
I'm sure your aware, but the 2020 Acadia has the new infotainment system, 9 speed transmission, push button shifter, redesigned hood and grille, etc. We debated about waiting for the 2020, but we didn't like the Terrain push button shifter that well and where the heated seat buttons were located vs. the 2019 Acadia.
2019 Acadia SLT-2 AWD, White Frost Tricoat/Dark Ash/Cocoa
2018 Terrain SLT 1.5L FWD, Ebony Twilight Metallic/Jet Black