Definitely all lower case is preferable. Forgetting about it considered as
shouting, it is all about the brain and readability.

When we read, the brain recognises most words by the shape of the complete
word. The brain rarely needs to examine the individual letters because as a
child it learnt the shapes of words. If words are suddenly all in Caps, the
eye has great difficulty reading the word shape, so it slows down reading
and causes reading fatigue.

Take simple word like 'stop'. The brain easily recognises its short length
and the position of its ascender and decender. Once you write it as STOP,
there are no ascenders or decenders to assist the brain, so it has to
actually look at the letters before recognising the word.

So never use All Caps - even in Titles if it is a long title.

Terry Farrell