They're both somewhat vulnerable to front element damage, as the elements are close to the forward edge of the housing; I always use a hood. If you really want pocketable, you need a smaller body than the P. If you want the Elmar, just bend the light baffle out of the way and move along - it's easily accessible from the front with the lens removed, and you can observe from the back (shutter on B) to make sure everything clears. As I said, the Summitar looks a bit more balanced on the P from a size perspective.
The Elmar is a very neutral lens - no peculiar optical characteristics, quite sharp from around f/5.6. The Summitar, aside from being almost two stops faster, can be a little wild in the out-of-focus areas. I love the Summitar, but some complain of distortion and swirliness. Acquiring a good example of either is a matter of either time or money; neither is rare. Much depends on how much speed you need and what your objectives are.