The Mahogany will sound a tad warmer vs. the Acacia, which will have a bit more (but not that much more) punch to it. I imagine they'll sound similar, though. Which one sounds better is 100% up to your ears. Other than the wood type, I can't figure out why the acacia is $100 more. If you are a Kala fan, I am sure you con't go wrong with either choice!
If you want to consider other brands in that price range, I'd look at Pono, Ohana, and Islander. Just above that price range are Romero Creations, KoAloha Opio, and Martin. If you want a uke of higher quality but don't want to pay that much, there are plenty of great options for sale in the Marketplace.
One more thing to consider is the quality of the pickup. While it may be more expensive on the front end, you may want to consider having a uke installed with a better pickup such as a Misi Trio or Baggs 5.0. There are plenty of threads on this board that explore everything I brought up.
Good luck with your purchase!