OK, I'll jump in first.
 
I voted as follows;
 
10 round mag is a turn off
Switching mags is important
Save up for the Subbie
 
Now for the reasons.  
 
I don't have a Hipoint nor have I shot or even held one.  I'm sure thery are good guns & from what I hear/read have an excellent track record as well as a Service department that may well be better than KT.
 
I do have 3 9mm Subbies, all S&W, as well as a 9mm Marlin carbine that uses the S&W Mags.  Any 9mm carbine I buy, with the exception of a Calico, Feather or some other exotic, would just about have to be S&W compatible.
 
Subbies fold in half.  I've got room in my safe for short guns.  Long guns not so much.
 
Hipoints are butt ugly.  OK, so I'm superficial, what can I say.  
 
As to the accuracy, I don't know about the Hipoint but if I want better accuracy than the Subbie I'll grab the Marlin.  I'd almost bet money that even if the Hipoint  is more accurate than the KelTec the Marlin has both of them beat.
 
The big issue, all kidding aside, is the magazine.
 
edited to add; I just realized this was for S2K owners.  I'm an ex-owner of an S2K.  But I do have four SUB9s.

Mag compatiblity and capacity, and the ability to fold give the S2K the edge over any other pistol caliber carbine, IMHO.

Before I got my S2k, I looked at the 995 and the ATI stock.  You can add a lot of cool stuff to it too.  However, the magazine issue swayed me as well as the 995 issues with the ATI stock, bent firing pins, and needing a tool to disassemble the weapon.  If they ever came out with a .45 HP I might look at that, but between the two, go with the S2k.

Collecting carbines IS just like eating potato chips.  You always NEED/WANT just one more.

Well, as the resident PCC junkie (I have owned 2 Hi-Point carbines in the past, along with an HK94, UZI carbine, and Cobray carbine, all in 9mm; I currently own 2 KT carbines [SUB-9 & S2K] along with 3 9mm ARs, 2 9mm Camp Carbines, a 9mm Storm, and others  ) I have to agree with this...
 
Quote from RAT76 on 08/29/08 at 10:33:30:

 
I consider high-capacity magazines a must (absolute deal-breaker) for any firearms platform I will (or even may) be using for anything more than just plinking; I also value magazine interchangeability much more than most do.
 
The two HP carbines I had worked flawlessly and were adequately accurate, and with the ATI stock (not on the market when I had mine) I could even live with the looks, but I just can't get past the magazine issues.  Very personal bias, YMMV as always.  

Quote:

 
Well, there goes the 1911 platform.  Headed for lo-cap mag oblivion.........................

I pride myself on valuing function over appearance, but I can't get past the look of the Hi-Point carbines. Aesthetics are very subjective. If the appearance doesn't bother you, then no problem. The Hi-Points are heavier, and I think they have a clunky feel but others probably perceive the same thing as the feel of solid reliability or quality. I'm an engineer and the Hi-Point looks low-tech to me, ignoring the aesthetics I mentioned earlier and looking more at the design and machining. I like the light weight of the SUB-2000. The S2K ergonomics do leave a lot to be desired. The straight bolt tube is an artifact of the S2K's ability to fold. To me, it's worth it. I love the little folding S2K. To my eye, the Hi-Point is ugly, but the S2K is "so ugly it's cute". Again, aesthetics vary greatly. YMMV.
 
I have a notebook PC carrying case. I put my PLR-16 in the main compartment, and the 9mm and .40 S&W subbies in another divided compartment, and a lot of magazines in an exterior pocket. I could probably carry six or eight SUB-2000s in a notebook PC carrying case. I think I'll test that theory at the Republican National Convention next week... not!
 
The subbies are remarkably portable when folded, and that opens a lot of possibilities where a pistol carbine is appropriate. You can take a SUB-2000 places a Hi-Point could never go - backpack, canoe, kayak, under a car seat, inside a winter coat, in a book bag in the summer, the aforementioned notebook PC carrying case, etc. To many people, that portability isn't important, but I like it. To me, a pistol carbine is an in between gun, when a pistol is too small and a rifle is too large. The folded subbie isn't much larger or heavier than a pistol, but the longer barrel delivers more energy and the longer sight radius makes it more accurate. If I was going to carry a big heavy Hi-Point, I'd get a rifle caliber rifle. In fact, I'd probably opt for an SU-16C and still have the ability to fold it!
 
Mag compatibility was apparently a big part of the value that Kel-Tec saw for the S2K, but it doesn't appeal to me as much. However, I greatly appreciate the ability to buy inexpensive high quality Glock mags instead of some expensive, proprietary, low capacity mags. Being able to use Glock mags in a Glock is a little bonus for me.
 
Basically, if you like the light weight and small size when folded, and can tolerate crooking your head sideways to shoot it, the S2K is a great little pistol carbine. If the look, feel, and weight of the Hi-Point don't bother you, it's a good choice. Like most things, what works best for you is determined by what you like and what you need. Choice is good.
 
I hope you posted a similar poll at the Hi-Point forum. No doubt they'll vote as heavily in favor of the Hi-Point.
 
Disclaimer: I'm cuckoo for Kel-Tecs.