Gary,
What is your intended purpose for either of them?
The .284 Baer will cost you more money and time. You will need to get a bushing die, as his reamer is a "tight neck", and you will spend time turning necks. Brass is also more expensive.
However, you will attain more velocity with it. You can run the 175 MK to 3200 with 83.0 Ret with a 28" barrel. Remember there are many variables in "accuracy", but time in flight over longer distances generally equates to more "accurate".
If you plan to shoot in competition, the STW will generally be easier on barrels.
If you don't mind the extra cost and work, go with the .284 Baer.
If you want a straight forward .284 with factory dies, cheaper brass, and less prep time go with the STW.
My 02 cents.
