The emnity on both is negligible since both WS produce a static amount of enmity and both are very low(coronach being lower) but it doesn't really matter because it isn't like your tanks wont be able to hold hate indefinitely off you for throwing the equivalent of a dispel at the mob every 4-5 shots.
If rng only I'd go with gun(if only for being more applicable with KC; you can't spam cannon shells w/o 100 alchemy or a good friend with it so you can stock your satchelplus, coronach for times where you want to ws at 100% mob health but don't want to tank is ftw).
If you also have sam I'd go with bow.
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