Forget the "mobile maps" version for android. That is old and and discontinued. They won't be developing that anymore or updating maps. It also has several issues with later versions of android and force closes.
The Aura now called Sygic Navigation is easily the best nav software and I've tried a few on the DHD. Though it is not free after the trial and can be bought.
That as far as i remember buys lifetime map updates. (uses tomtom maps).
Also they frequently do discounts as well as a 25% off voucher when you purchase. These last a week or so and there is a forum where people post these if they aren't using them, so others can on their new purchase.