Just in general - is there anything in arc which gives it a big edge to programmers when compared to clojure?
Here are some of the differences, but I can't tell if one of them is crucial. I listed three below for which I've no clue what the impact is.
* The read table is currently not accessible to user programs
* Keywords are not Symbols
* Symbols are not storage locations (see Var)
* immutable data and first-class functions
* *first* is clojure's *car* ;)
Oh, Clojure is not quite completely immutable. Clojure has refs, and they can be mutated within the context of a 'dosync form. Kind of like the Haskell "do" syntax. It's more that Clojure defaults to immutability, and has special syntax to define portions that are imperative.