The Summicron is lower contrast, will not look as sharp. It will preserve more shadow detail.
If you can find a collapsible Summicron in good condition, also look at it. Cost about 1/3 less than a Rigid. Not quite as sharp, but close.
Some shots with my Collapsible and Type I Rigid Summicron on the Leica forum, here:
Hopefully you can see the images. If not, register for free and then you can view them.