Pros:  Extremely fun to shoot FA.  Investment-wise, value can only go up since there are only a finite number out there (talking firearms only).  Looks cool as shit in your safe.

Cons:  Money- te initial investment is steep.  Propensity to want more.  Constant daydreams about getting to the range and emptying a mag.

Is is worth it?  YES!!!!!!!!!!!!!!!

Edited to say I'm an idiot for not reading the question thoroughly.  Thanx Shaggy for answering the question- I just saw "CLASS III".

Pro's - By going corporate, no CLEO sign-off to deal with.  Slightly faster transfers (or so I'm told).

Con's - You MUST keep the corp alive - this may include filing corporate taxes, annual corp fees, corp/business licenses, etc.  You get around the CLEO signoff, but there's other paperwork and possibly fees you have to deal with on a more regular basis.

If you already have a corporation and that corporation does anything else (actually engages in some sort of business) for which there may be some liability issues, the guns are corporate assets and can be used to satisfy debts/liabilities of the corporation (if your corp gets sued).