While I don't have a 750-DI or it's predecessor the 750, I have looked at a lot of rotators (my term) and comments/reviews for same. Surprising how many people claim good service in hard use from this type of vise while others show broken jaw pix. Cheater pipes aside, this makes me suspect not only are the castings necessarily thin but there is a greater frequency of defective castings in this design. Yet there are good ones to be had.
There are at least three to four sizes of rotators. Some are advertised as heavy duty - a relative term to be sure - yet at least some of those actually are thicker/bigger and do seem stronger than the cheapest style.
You have probably noticed this in the description of the 750:
"Vise intended for
general purpose use since it is made from grey iron. Vise is not designed or intended for industrial / heavy duty demand applications. For increased demand applications use Model
865-DI,
65C, or
32C. Contact factory as needed."
Yost seems to be stating the 750 is a light duty vise (it's easy to break?) whereas the 750-DI is "Made of Heavy Duty Ductile Iron".
Here's something in the 750-DI description that is important to me on any vise with a swivel: "Vise body rotates 360° using
interlocking V-grooved swivel base (emphasis added) and (2) two lockdowns to lock at any position".
If that means the swivel positively locks with gear type teeth like the US made conventional Yosts, then this 750-DI may be the only current rotator that does that, aside from possibly Swinden.
Amazon advertises the 750-DI for $275 shipped:
http://www.amazon.com/dp/B00CBL62HQ/?tag=atomicindus08-20
FWIW, if I didn't already have a Charles Parker rotator (sheer luck I ran into that locally), I would get the 750-DI.
Best of luck to you. Please report back.