rpeter . . . based on the posts, you can see that there is some bias in favor of "captured" lower link pins. For the most part, only light duty models do not have this feature.
Weight is also important with a box blade, within any given size range, the more weight the better. For example, MIDWEST makes a 15-series box blade and a 20-series box blade, both are available in a 48" size. The 15-series is sold for Sub-CUTs and the 20-series is for CUTs, the weight difference between the 2 blades of the same brand is nearly 100# with the 20-series being heavier.
I like the side plate shape of the Midwest brand blade, but really it only offers a minor advantage over the designs with a clipped corner. I believe some of the Gannon blades (made by Woods) also have the same side plate shape that Midwest has. High on my list of desireable features would have to include easy to adjust scarifier teeth. I want to adjust everything without the use of tools and I also want to be able to adjust things while wearing gloves, even I don't always wear gloves, if the parts are big enough to grab with a pair of gloves on, then they are typically easier to engage/disengage.
For what it is worth, I bought a model BB20-48 48" Midwest this spring. I was quoted $400 from one dealer, $420 from another. If I recall correctly the Buhler/Farm King 48" BB was quoted at $435.