Isabel, contact Kari Smith, who's certainly been around both styles.

For what it's worth, here's some second-hand info: I have a friend who's seriously dance-eclectic. He's working on tap now, after years of various folk styles, including clogging and French Canadian step dancing, but especially international folk dancing (e.g., especially Balkan). He says tap has been a struggle for him to adjust to, because the center of gravity of your body is in a very different place. What I've seen of English clogging, it is very similar to tap. So... draw your own conclusions, but I'd talk to Kari, first. I've got an e-mail address for her, if you want to PM me.

~ Becky in Tucson (with my cookie back)