CTT probably initially would be higher.
However, what will get you the high pay is probably the clearance, and you'll keep that anyway. You can get some certifications for specific programs/systems via IT, and those are worth money.
If you stick around to go IT...you're probably looking at going the long haul. If you get out at 20...you're probably looking at the same jobs no matter what (or the very least, the same job fields), since it will be your overall experience and management skills that they are looking for at that point, not necessarily specific technical skills).