The HR version includes the heart rate feature that the regular Alta version do not have. Specs in the product page or in Fitbit website https://www.fitbit.com/au/shop/altahr
Previously posted on 08/10/2018 at https://www.ozbargain.com.au/node/407760 (expired) but they are still selling for the price $138 which is around $62 less than anywhere else. I have just got one for my dad using click and collect from Clarence St Store.
JB will have it for $99 from Friday according to their catalog. I think I saw a post here already.