Too late I guess, but did you check which type of plane TK is using between IST and GVA? They have some short haul planes with real business class seats (on A321s). But if you have to fly IST-GVA in a normal economy class seats the shorter TP option looks a lot more interesting. (I know that TK is considered the better airline, but I have never had a problem with TP - I have always enjoyed flying with them.)