Tac-Girl,
Let me make a minor assumption--you are in a state that allows AR's or HK's (not California).
Do you have any possibility (or desire) of getting a full auto in the future (assuming your state allows it)?
Let's say you do.
That would be the main reason to buy an HK over an AR. With a registered HK sear, you can have a full auto gun in several configurations (or even several calibers if you move it from gun to gun). An AR's mags are about 1/3 to 1/4 the price of an HK's. I like the idea of keeping all one type of mag in a given caliber (keeps things simple). The HK is also relatively heavy for a .223 gun.
One other possibility you forgot to mention is an FNC. Caliber .223, most of them are folding stock versions, works extremely well, and there are auto-sear's available. It also takes AR-15/M-16 Mags.
FNC $2000
HK 93 $2000
AR (pre-ban) $1000-1200
Autosears
FNC $1600
HK $4000
AR (DIAS) $4000
Makes the FNC the best deal in a conversion gun.
FNC:
[img]http://albums.photopoint.com/j/View?u=1157297&a=11109695&p=44316138&Sequence=0&res=high[/img]
Of course, you can do this with the HK and sear:
[img]http://www.hkpro.com/image/HK53A3left.jpg[/img]
The conversion to an HK 53 will cost about $1000.
AFARR