Upload & Sell: Off
Thanks all for the great resources and real life experiences. Looks like the Marshall 7" is on sale and uses the Canon batteries which might be a nice convenience.
I have one coming today but I intend to use it primarily for video. From the reviews on the B&H website, it seems to work well outdoors even in bright light which is a major issue with the camera's own LCD.
You can get a hood, but my experience is the glass on the camera's LCD at least reflects back whatever is opposite it - such as the shirt I am wearing - much more than the sky, so I have taken to wearing black shirts - even in the heat of summer - to minimize reflections. I'm not sure if the glass on the Marshall LCD is as bad, but I do think the larger size will help either way.
In terms of turning it off for composing your shot and then just using it to review your photos, I guess you can plug and unplug the HDMI cable or remove the battery on the LCD (from what I gather from the BH customer reviews, there isn't an on/off switch per se), but that would quickly become a PITA and I'm not sure why you'd need to do it anyway. Assuming the image is visible in bright sunlight, focusing with Live View is fine and seems preferred to looking thru the camera's viewfinder to try to compose your shot.
Anyway, I'll try to check back once I receive and test the Marshall LCD.