I think both of them have a similar meaning but the use of んスカ is puzzling, like what is the literal translation of it?
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It's a bit difficult to answer without knowing where you saw these, perhaps a bit more context might help? – user36788 Feb 29 '20 at 2:17
Sometimes です can be abbreviated to す or っす, as you seem to have guessed. There is an answer here about that: