Hi Guys:
These ones, and the first one Frenchy posted, are the ESV variant, which is the purposebuilt engineer variant. They can carry a variety of blades/plows. An indication of the ESV is the attachment on the bottom of the front hull (jettison fitting kit) which allows the many types of blades/plows to be attached as well as providing hydraulic power, the missing slat in the front of the ESV, and the lane marker boxes on the rear corners of the ESVs.
The Blast offering is something that is locally designed by units to be used by non-ESV Strykers. I suppose there aren't enough ESVs out there with blades.
Something I noticed in Frenchy's photos is that the Rhinos on the ESVs are not centrally mounted, but off to the right side.
Bob