.I'm going to call this black-bordered clamshell version "very rare" since I've never seen it before. The "bigger explosion" cover below seems to be the one that became much more prominent. So much so I have five or six copies in fantastic shape and see it around more than any other Thorn EMI title. It wouldn't be surprising to hear this film was the biggest seller/renter in the distributor's history...with the latter design.
Both releases have matching catalog numbers (TVA 3002) and cassette labels. The only thing I can surmise is that the black cover was the initial release with the explosion cover being quickly favored by Thorn EMI and mass-produced over this disregarded first design. The second cover is more eye-catching and zooms in on the still of Stallone so it would make sense in terms of marketing appeal. What also helps support this assumption is how their clamshell of First Blood advertises the upcoming video debut of the sequel with similar artwork.