Time for my $.02, so cover your eyes.
The ONLY reson to buy a 733 is if you are completelely BHD-OBSESSED, and/or like guns that were used 10 years ago. Now before you all jump on me and remind me that 733s are still seen in a few units these, days, don't bother, I already know. The fact is the 733 has no removeable carry handle, and has no battery upgrade option, other than a battery bag. Not cool!
The right choice would be to get some brand of M4A1 with a RIS (or RAS, whatever), SIR, ETC, or SOB, and get a shorter barrel kit. Do some REAL M4's have short barrels? YES! Does it look kickass, and come in handy in tight spots? YES!
BTW, that rail system, other than looking cool, provides many battery storage alternatives, including the ever-popular fake IR units (ie AN/PEQ-2 [NOT spelled AN-PECK!]). If you want a surefire for that 733, where ya gonna stick it? Ok, on a barrel mount. That Aimpoint? Fine on a carry-handle mount. A bigger battery? Whats that you say, A BAG?!? Catch my drift? You can only go so far with the 733 and no rails. Besides, who doens't want to have the latest and greatest SOF weapon this side of Ft. Bragg?
As for its perks, it has an EG1000, v2 box, and looks like "Hoot's" gun (for those who give a damn). It's also nice and short, and is a really cute piece of plastic (yeah, I said CUTE!).
END EDITORIAL.
Cheers, lads!