Ok, I've been looking around a little more. I was right the first time. It's this:

17-50mm Di original which uses screw-drive AF, no BIM, no AF switch. Model No. A016
17-50mm Di-II which has a built in motor, AF Switch, identical optics. Model No. A16NII
17-50mm Di VC which has VC, built in motor, AF Switch, slightly different optics. Model No. B005

None of them have AF override.

Presumably, the op doesn't need any more advice, but in case anyone else uses this thread to look for more opinions, I'd like to point out Roger Cicala's opinion on these two lenses in his blog post (search for "Stuff I'd wish I never bought"). In this case, it appears that the optics of the VC and non-VC lens are different.

I have been trying to find out all the versions of this lens. AFAIK there are three:

17-50mm Di original which uses screw-drive AF
17-50mm Di-II which uses a built in motor, identical optics
17-50mm Di VC which has VC, slightly different optics

Please correct me if I'm wrong, I couldn't find much info on these lenses, especially the original.

Thank you TaoTeJared for your honest and clear advice.

I have researched these two and almost bought one but decided to move to FX and spend my $ on FX glass.

Short story - the IQ is the same if not better on the VC version.

What I found:
After reading endlessly and every article I could find the end result is that they have the same IQ and the VC for hand-holding gets you about 2 stops. The few tests that said the IQ was not as good on the VC version were using the lens on a tripod with VC ON which goes against the Manufactures recommendations. The Cannon version on one review site went bonkers with the test results and the review went back and re-tested with the VC off, mirror lock up on and the IQ scored higher.

What I learned from this experience: Reviewers need to write something to keep people coming to their site.
What is hard, is to review two lenses at the same time. When most are testing, they are provided a sample that they send back making testing both at the same time rare. Almost all the sites tested these lenses 2+ years apart, some on different cameras, Different software, and not always with the same settings.

Every reviewer site has preferences towards; Manufacture or 3rd party, VR(VC,OS) Vs. Non VR, Prime vs. zoom, FX vs. DX, etc. We even see the preferences on here between everyone. What I look for is when people do a comparison between lenses, if they are splitting hairs, that means either are a good choice.

I have the original version (non-VC, screw-driven AF) and it's very sharp—it's my most-used lens. I don't have experience with the VC version but I actually agree with heartyfisher. Chanpo is right that VC will not help you stop subject motion, but both lenses have the same max aperture so you don't lose anything as far as stopping subject motion and you gain the vibration reduction. Someone here on this forum got a sharp copy of the VC version: http://nikonrumors.com/forum/topic.php?id=1985

The VC version wasn't available when I got mine or that's what I would have gotten. I'm actually hoping the nikon 24-70 gets VR. That would be my dream lens.

I greatly appreciate the insight but I am now torn. Vallon votes to get the non-VC and heartyfisher says to get it. ???

chanpo said:
Rummer, which one do you have? A16N or A16NII? I want the non BIM version A16N but can't find it brand new anywhere. May settle paying $330 on eBay for a used one.

I have the A16NII. I checked out a few stores here in Tokyo, but I haven't seen any of the original A16N.

chanpo said:
...
I've been told the IQ for the non VC lens is much better. Also heard that the version without the built in motor is faster, quieter, and more accurate during focusing.

...

+1
Thats my understanding from my research as well..

to OP if you are taking a fast moving object in dim light then VC wont help much. but I believe the IQ difference is not so bad that you would choose between them just because the VC version is slightly worse. 3-4 stops VC is nothing to sneeze at. overall I think the VC version is well worth the difference in price and reduced IQ.

I've been researching these 2 versions for a while now. I figured with the VC version being newer, it's gotta be better. However, after all the research and reading, I think I will end up getting the non-VC version, sharper than the new version. It's around $414 after rebate.

With this lens being so versatile, I would not get it used. It's probably the most used lens in a photographer's bag, so you would be rolling the dice hoping for a well-cared used lens.

VC is for stabilizing the image when the shooter is moving, not when the subject is. To avoid blur when shooting your kid, increase shutter speed. VC isn't necessary and I've been told the IQ for the non VC lens is much better. Also heard that the version without the built in motor is faster, quieter, and more accurate during focusing.

Rummer, which one do you have? A16N or A16NII? I want the non BIM version A16N but can't find it brand new anywhere. May settle paying $330 on eBay for a used one.

Thanks for the tip. My main use for the lens is taking pictures of my 2 year old son that never stays still. I think I am going to get the VC just in case.

Hey elopomorph,

I just shot a wedding using the D90 and the Tamron SP AF17-50mm F/2.8 XR Di II (non-VC version). I'm no professional photographer, but I got some very sharp photos. There were times when I wished I had the VC though, especially when the environment became dark, and I didn't want to go above ISO 800. Depending on what you kind of photography you intend to do with it, you may be fine with the non-VC version. If you think you may use it for weddings or in dim settings, I would suggest you go for the VC version.

I am going to purchase the Tamron SP AF 17-50mm f/2.8 XR DI-II lens for my nikon D90. I don't know if I should get the one with VC (Vibration compensation) or without VC? The one with VC cost $100 more.

Will VC make much of a difference for a 17-50 mm lens?