There is no need for last round bolt hold in USPSA. Maybe IDPA, not sure of the rules in that game, if they still require 'slide lock' reloads in PCC...
To be competitive in USPSA PCC you will need and endless supply of ammo in one magazine. With the mostly adhered to maximum of 32 rounds a stage, you will want a dependable 40 round magazine. With 40 rounds on tap you will have extra rounds to hose away with. There are several sources of reliable extensions to achieve 40+ with a glock 30 round stick. RELIABLE is the key word.
Glock mags are the way to go, and the Ruger PCC is the only (sub $1000) glock fed lead dispenser that I consider capable nearly out of the box. Its trigger is good enough as is, its recoil is mild, it is lightweight and balances well. After installing a DPP or RTS2 on a barrel mount, buy Taccom upgrades as money allows (mag release, magwell, muzzle brake...)
Mag release and magwell will only improve your times where a mandatory reload is required, again, glock mags excel here.
Colt smg / modified uzi mag fed AR:
There is so much variation in manufactures of these mags combined with the slop in the adapters used in an AR pattern carbine, its amazing I got 6 out of over 30 magazine tubes to run reliably in my 3 seasons of shooting them. The double feed (vs glock single feed) is the issue with these. The height of the magazine relative to the feed ramp / barrel is super critical. They are also sensitive to bullet profile and cartridge overall length.
Keltec:
The only good thing is it can be had in a glock mag model. I see it as a novelty fold-able carbine. Great for backpacking or hiding under the seat of your car and having magazine interchangeability with your pistol. No great way to mount an optic. Ergronimics are horrible.
Scorpion:
Its a little heavy. The mag release is funky. The trigger sucks. Its very difficult to successfully seat a loaded magazine on a closed bolt (on a required reload stage) As far as I know the only trigger upgrade is from CZ custom and its quite expensive. +10 extensions are available for the 30 round mags but will need tuning.
MPX:
Pricey. 1st gen had lots of problems. 2nd gen still had problems. Heavy, needs an aftermarket trigger, but while also pricey, the mags are good. I am told the new 3rd gen PCC model is much better, lighter, not sure about the trigger.
AR varient:
Glock mag fed over any other. Endless possibilities available in factory complete carbine or assemble yourself. A factory complete quality carbine will be over your budget 1500+++ ( Limcat, JP, MBX) budget factory carbines are out there, but IMO not worth it when the Ruger is $500. If going the assemble yourself route, be prepared to spend extra money, time, and alcohol tinkering.
I've only shot the gun before. Never owned one. 
