I use Avenza for GPS and maps. App is free but most of the useful maps cost between $2.00 to $8.00. I think Whitney Zone map was over $7.00.
I have not used anything else so hard to comment on how it compares.
But I found it very useful on my hikes and as long as I had the map downloaded it seems nearly impossible to get lost... as long as your battery doesn't die.
