They are different as night and day. The V67 has a very contoured sound to it while the 2003 is much more neutral in character. The 2003 is more or less flat until you get way up in the high range, then there is a boost. It'll give you more "air" in your sound. See the frequency graphs an the MXL site to get a mental picture.
I'm sorta with Chessrock on the V67. It doesn't work on everything, but when it does, its fabulous. I have made very fine takes on several singers with the V67. Its a great voiceover mic too. Interestingly, I was watching The Clone Wars on my computer the other night and monitoring the sound track through my NS 10's. As you probably know, most of the dialogue is overdubbed in films. Well, I started listening to the sound of the dialgue tracks and my first thought was, "Man, that sounds just like the V67!" It was probably a Neumann--but who knows for sure?!
In my book, I consider the V67 strictly a vocal mic (and voiceover mic) while I see the 2003 as being more versatile for different sources. It works on acoustic guitars, electric guitar cabs, a good percentage of voices, and percussion. At least thats what I've used it on.
I wish you could try the V67 on your voice before you buy. If it works on your voice, you'll love it. Heck, I wish you could try them both, but, then...you might want one of each!