The BM 300 doesn't look like it has enough detent strength to build up enough energy for proper deployment without wrist flicking; a downside for some. Also no titanium slabs/liners if that matters to you. The Southard is worth the $230-$300 most places are asking for. The quality, heft, and solidness took me by surprise.
The only weakness that I see in the Southard is the clip design. Aesthetically, it could have been designed better - preferably with titanium. In addition, the tip of the clip should have been angled slightly higher so as to avoid snagging on clothing when trying to clip into the pocket. Furthermore, it has slight yawing movement along the scales when medium pressure is applied. (like the wholes were made too big for the screws that secure it to the titanium slab).