This is a nice addition from Victron that solves strain relief and somewhat protects the wires. It's effective at strain relief but if you use the largest cable gauge that the solar charge controller will accept then it's hard to put the cap on the wirebox. There's just no room between the wires for the *****. Smaller wires will work just fine.
As far as protecting the wires there shouldn't be a need if there are no exposed strands (the insulation has been stripped back, but not too far back).
A downside of the wirebox is that it takes up more room. If you're cramped for space like I am in my RV, space is a premium and the extra couple of inches it takes up isn't worth it.
As far as aesthetics, the wire box looks very nice.