A traditional Reuben sandwich uses Swiss cheese, but my take uses mozzarella which I find a bit tastier.
This is one of the most delicious rueben sandwiches that my family has ever tasted! PUt the sandiwch under the broiler. It is even better. YUMMMMMY - 08 Oct 2001 (Review from Allrecipes USA and Canada)
Mozzarella cheese doesn't really have much flavor. I don't consider this a Reuben sandwich since it doesn't have Swiss cheese and Thousand Island dressing. It has a nice little flavor in itself, but true Reuben lovers will know something's missing. - 30 Oct 2002 (Review from Allrecipes USA and Canada)
The mozzarella does not compliment the corned beef...swiss cheese is really the best way to go. - 17 Aug 2002 (Review from Allrecipes USA and Canada)