The Sigma block in the SigT is the same as the SX1 and SR2.  The new Atomix cover is the secret.  It is cleaner through the front and more angular on the back.  If there was any way to improve the SR2, the SigT does it.  It retains the readability of the SR2 but hooks a bit more and in different places.  Carry is as always superb.  They respond to various patterns excellently.  I haven't experimented with surface adjustments yet.  I start with a Raptor and ball down to a strong SigT, then go to a lengthier SigT, then drop to the Backdraft, then a Recon.  The Raptor/SigT/Backdraft combo is formidable.