Which is better for gaming?

The Samsung M70H. It adds Motion Xcelerator with DLG 120Hz and variable refresh rate from 48 to 60 Hz, plus Gaming Hub. The Vizio MQ6 is a 60 Hz set with no gaming features listed.

Which has better picture quality?

The Samsung M70H on paper. Its edge-lit Mini LED backlight and HDR10+ support give more brightness and contrast than the Vizio's standard QLED HDR. The Vizio holds a wider viewing angle.

Which is better for a bright room?

The Samsung M70H. Mini LED backlighting pushes higher brightness, which helps in daylight. The Vizio QLED is dimmer by comparison.

Does either include a wall mount?

The Vizio MQ6 lists a wall mount in the box. The Samsung M70H lists a stand and remote; a wall mount is not included.

Is the Samsung worth stepping up to?

Yes if you want voice assistants, Bluetooth, Gaming Hub and free live channels built in. If you only need a basic 4K QLED panel, the Vizio covers that.

Which has more HDMI ports?

Both list three HDMI ports. The Samsung adds CEC, Bluetooth and Wi-Fi 5; the Vizio lists Ethernet and CEC.

Samsung M70H Mini LED 4K TV vs Vizio MQ6 4K QLED Smart TV

Buy the Samsung M70H if you want the smarter, more connected TV: Tizen with Gaming Hub, Samsung TV Plus, Google Assistant and Alexa, Bluetooth 5.3 and Wi-Fi 5. Buy the Vizio MQ6 if you want a straightforward QLED 4K set with a wide viewing angle and a wall mount in the box. The Samsung has the edge on features and processing; the Vizio is the simpler, no-frills panel.

Choose the Samsung M70H if you want built-in voice assistants, a gaming hub and free live channels without a streaming stick.
Choose the Vizio MQ6 if you want a basic QLED 4K TV with wide viewing angles and a wall mount included.

Prices

Samsung M70H Mini LED 4K TV: $377.99 at ABC Warehouse (last seen Nov 4)
Vizio MQ6 4K QLED Smart TV: $298.00 at Walmart (checked today)
Difference: the Vizio MQ6 4K QLED Smart TV is $79.99 cheaper than the Samsung M70H Mini LED 4K TV at the latest prices (Nov 4 and Nov 10)