You don't need a $200 stamp to run a braced pistol, so the cost of a braced $750 pistol is approx. $875 (KAK) to $950 (SBT EVO) $1050 (Tailhook).
I was going to get a carbine and cut it down to be an SBR, but after shooting the braced pistol I realized that I wouldn't like the longer barrel nearly as much. The Scorpion is a mean little bugger of a pseudo-SMG, and the carbine wasn't what I was looking for. With all the brace options and developments that have come out since then I'm pretty happy with my decision.
The major thing for you is that my local USPSA, steel challenge and action rifle matches (indoor leagues) won't allow braced pistols to run as PCCs. But I would check as I'm not sure if that's regional or national rules. With the changes to the legality of shouldering, this may change too. Liability for prosecution for (at the time) illegal shouldering was the most common reason for banning them I heard.
Pros for braced pistol:
1. Way lighter and handier
2. Looks awesomer (my opinion)
Pros for Carbine:
1. Legal for USPSA, steel challenge, etc.
2. Can run VFGs
3. The factory stock is better as a stock than any of the braces
4. Way better factory handguard (I wish they'd done the smooth-sided M-lok thing on the pistol. My HBI handguard is out for delivery today.)
5. Not subject to the whims of the ATF with respect to shouldering
If cost is a concern and you think you want a pistol, keep an eye out on the used market (classifieds here, AR15.com, etc.). I bought my Scorpion from a friend who bought it, kitted it up, shot 150 rounds and sold it to me for a great deal. I've likewise seen some incredible bargains on very lightly used or unfired guns on this forum's classifieds.
William
William