Neither.

But the tram passes right in front of HI.

For sightseeing, you would be much better off to stay in local hotels in the Sirkeci area - walking distance to Hippodrome to the north (uphill), and the water front to the south (downhill). Both are just one tram station away if you dont want to walk. Topkapi Palace (now a museum) is half way before you reach Hippodrome. Easy tram + metro ride to / from airport.

http://www.turkeytravelplanner.com/g...bul/index.html

Although I dont know how much you could accomplish in terns of sightseeing for just an overnight.