Take the shorter connection if you decide to fly QR. The premium terminal is ok, but really not that special. If you hit the evening departure bank, you might have trouble finding a place to sit down like I recently encountered.

For 6 hour transit I would leave the airport and go to the architecturally stunning Islamic Museum and to the souk on the other side of the road from the museum.

The Premium Terminal is WAY overrated. I cannot wait for the new airport to open. I have EIGHT transfers coming in Doha in the next two months or so.