Original Starfires were all SF2 ready,and did not include the tilt module unless it was added later to the bottom of the receiver.

ITC receivers can be bought either SF1 ready or SF2 ready.($2500 or $4500) ITC's all come standard with tilt correction.

If you have a GS2 display,many more diagnostic pages are available with the ITC receivers.

Original receivers weigh about twice as much as ITC's.

ITC offer a few added features as far as RTK,ie 12 miles of working radius if an ITC is used a base(i think that is correct)