Better Quality = More Durable; I don't believe inside vs. outside opening tools have anything to do with it.I do think outside opening tools have two distinct advantages though. First, the tools are quicker to access because one doesn't have the added step of opening the handle first. Second, when using the pliers, one's hand is on the generally smooth part of the handle, as opposed to pressing on the backs of all the closed tools as with inside opening tools.Never trust a lock if you value your fingers.
Would you consider a tool durable if it could fail in a dusty/dirty environment?
I just wish the manufacturers would indicate the "suitable environments" so one knows beforehand.