I bought the Field Pro version about 15 months ago - exceedingly happy with mine. The Field Pro also has a slightly different lock on the dioptre adjustment and is arguably slightly more secure than the previous version, but it wouldn't be a deal breaker - the previous was fine.
Personally, I think the case that came with the previous version was better - more substantial and with an internal divider and pocket. The new case only has an open external pocket, and in my experience, the zip to the main compartment is not as easy to operate when the case is worn over the shoulder. I took this up with Swarovski, and they very kindly provided me with an older version. Incidentally, I have a feeling that both of these cases are made for Swarovski by Crumpler who make excellent quality camera cases - many of the construction details are similar, and the rather distinctive font used on the internal labels in the cases is identical.
If it were me, my choice would partly be governed by the price you're offered on the older version. Either is a superb instrument, and I think you'd be very satisfied with which ever you choose.