For most street driving conditions, even snow driving, 4-Lo will be way too low. I have yet to meet a snowy road that I couldn't tackle in 4-Hi (I live in hilly MD, we've gotten blasted for the past 2 winters.) Maybe some extreme updhills would call for it?
I have only needed 4-Lo for off-roading. I use it to control speed on rocky or muddy downhill decents.
Besides, 4-Hi is shift on the fly, so as road conditions change, you can go in and out of 4WD as needed. 4-Lo requires you to pretty much stop (or slow to less than 5mph, can't recall?) Not so practical for street use.
Not sure if that answers your question. Just my 2 cents.