I have not used the Kirschbaum syn gut. I have used the TF and Gosen. The Tecnifibre Syn Gut plays very firmly and lasts about an 1 and a half to two hours for me. I bought a reel of the black a while back and it can be strung IMO a little looser due to its firmness
Gosen plays much softer. I liked the feel, but probably should have strung it tighter as control was lacking.
IMO, Babolat SynGut is the best of the bunch (even though you didn't ask about it). The big downside to it is 2X the cost of the other two and it goes really soft after a couple of hours but breaks to make up for that.