If you will be flying from Hiroshima or Itami, then Hokkaido might be interesting and beautiful. If you will be traveling by train with a Rail Pass, I'd say forget it. That run from Hiroshima to Sapporo would have you on 3 or 4 different high-speed trains for 14 to 17 hours. Even if you stopped at Hakodate instead, it would be 3 trains for 11 to 14 hours. Not worth it.

If you choose Sendai, there are several reasonably priced hotels very near the station, making it very easy to get around the surrounding area by train. Last fall, I used the Comfort Hotel West (there is also a Comfort East), which is about a 5 minute walk from the main station entrance, less than 10 with luggage. There are others of varying quality equally nearby. I chose the Comfort because I wanted the location plus free wi-fi, free breakfast, queen beds and on-site coin laundry facilities. YMMV.

If you are interested, several months ago I posted a thread and link to some photos I took last fall, including some of the Sendai Station area and a couple of day trips from there. Link: http://www.flyertalk.com/forum/japan...olor-trip.html .