Thanks Cliffy - and everyone else. This DOES make sense.
So the DriFit shirt should be reserved for rainy weather when I need to dry out quickly and the long-sleved Merino wool shirt is what I want for a sunny day.
Yay! I can't wait to see how disappointed my riding partner are when I stop wearing wet t-shirts. ; )
It's a Kawasaki WTF650R. And sand is evil.