Winter cruise from Rausu or Abashiri?

I'm just making plans for a 2017 trip to Hokkaido in February. Of course I want to go the Sapporo and other sightseeing spots on my journey, but I want to see drift ice also. I read about cruises to or through drift ice from the northern coast of Hokkaido, but I'm not sure which one to suits to my interests more or if I should take both cruises.

I've seen pictures about the Rausu cruise where lots of sea eagles are shown. They seem to be feeded so I suppose it's quite common to spot them on that cruise from a close distance. Taking pictures of the eagles is one of my major interests. On the other hand I'm not sure if its a drift ice cruise or just a cruise to the borders of the drift ice.

I've read that the Abashiri cruise also tells about sea eagles on its website, but the cruise ship seems to be large, so I suppose there is not a very good opportunity to see the eagles from a close distance. On the other hand, this cruise seems to go through the drift ice an not just to the borders of the drift ice.

So maybe I have to take both cruises if I want to have sea eagles and drift ice?

If Rausu is recommended, how is the best way to go there? I plan to get a rail pass for the journey through Hokkaido and maybe rent a car from Abashiri (or from Shari if its possible). Is it recommended to go to Rausu and maybe Utoro from Abashiri by car in wintertime? Public transportation seems to be very limited to this time of year.

Thanks a lot for your advice!

I'd like to mention that I would be glad about information about car rental options and February street conditions around Abashiri / Shari / Shiretoko also.

Or if you have taken part in one of the cruises, please share your experience.