I'm gonna vote for the Sputnik for 3 reasons.
1. It's a higher grade steel than the others. (Jamis is one of the best brands for steel MTBs out there FYI)
2. The dropouts are forged (see image: http://farm1.static.flickr.com/147/3...7b1304.jpg?v=0). That will make for a much nicer ride.
3. The Steamroller - which seems to be most peoples choice - is much more common; you'll see far fewer Sputniks out there.

EDIT: Here are a few more reasons:
The Jamis will be ligher - it has a carbon fork.
It comes with 2 brakes.
It comes with both a freewheel and a cog.
It comes with more practical handlebars with hoods - essentially giving you drop bars and bullhorns.
The seat also looks much nicer...