I would prefer the M5 Lite for the following reasons:
1. Larger screen - more real estate for movies, pictures and even reading on the internet.
2. I think the M5 Lite is cheaper than the M5 8.4.
3. With stylus support, it can be re-purposed for HBL, since can do homework directly on the device. Very good for kids in school. Don't need to print, do, then scan again. Very painful!
4. Better speakers, very good for online lessons, clearer audio is very helpful. HBL is here to stay.
Some cons:
1. M5 Lite is considerably heavier. If you hold it often, it will tell on your wrists and fingers.
2. I think the M5 8.4 has more powerful processor?
So M5 Lite for me. I prefer larger tablets. That's the whole point of a tablet. Otherwise a 6.5 inch phone will suffice...
Just my 2 cents... hope it helps you!