This comes down to you, and what you want it to do.

Based solely on what you have said you want to use it for, if the EMT shears cover all your other needs, the box knife fits best.

This is just about you.
Dozier is a great knife. If you get that, find a cleaner, rubbing alcohol/ goo gone to clean it regularly. You will have issues sharpening with Tape glue on it.
It will be more versatile than the box knife, but more work.

Swiss Army with a locking blade is a great tool, if you need lots of versatility. ONLY thing bad is that lack of a clip, so you need a case, or not mind digging in a pocket.
same comments as above, Goo Gone, more versatile, more work.

Just to go in a TOTALLY different direction-- taking this to the logical extreme-- have you looked at something like this?

Sparco Fast-Point Snap-Off Blade Knife
The item is 43 CENTS, Heck, the item costs less than the replacement BLADES, lol. The snap off blades have 10+ sections, so you can snap off the dull piece. At the price, you could buy 45 of these for 20.00$
If ALL you need is box opening, they are Light, Cheap, Pretty Safe (Very little blade exposed)
They are designed for the job you specified. Specialized.

In the end, what do you want?