I've been using rubber lens hoods for a few years and have only found two drawbacks.
But overall they give me more confidence that the lens won't get hurt (thick rubber after all)
and that the lens hood won't break or get lost.
And they let me stuff my long lens in a camera bag without taking the hood off.
The lens hood just smushes up (technical term) nicely.
1. They do "vignette" (meaning corners tips are solid black)
if you don't adjust them carefully.
They have three settings so you can back them off to eliminate this "vignetting."
2. They are so cheap, I'm trying to cut the rubber to mimic the lens hood
"leaves" or petals from the plastic wide angle lens.
The bother is that these hoods screw on so they don't always line up
exactly where they were when I cut them. (Hint to manufacturers: I'll
buy several if you can do this for us.)
The bottom line is I use the rubber lens hoods 95% of the time
over the perfectly good plastic hoods that came with the lenses.
The remaining 5% is for wide angle when the sun is right on the
cusp of lighting up the front lens.
Here's the 77mm version that I use.http://www.camera-filters.com/index.php?main_page=index&cPath=483_724