I've been using Tower for a few months, GitHub.app for a few minutes. Tower makes a lot of sense if you understand how Git works--it uses the same vocabulary (branches, remotes, fetc/push/pull, etc.) and encourages the same workflow.
GitHub.app seems like it's trying to take some of the complexity out of Git for beginners. For example, I'm looking at the "Changes" tab and don't see a distinction between staged and local changes. There's just a "Sync Branch" at the top that presumably does a pull, you don't get to have multiple remotes, just a "primary remote repository". No --rebase on pull, either.
Basically it looks to me like GitHub.app is trying to make common scenarios a lot easier to understand, but you have to go elsewhere for anything even slightly outside the lines. Could be the right tool for getting Git newbies (or even VCS newbies) onto the Git/GitHub wagon, especially for those who don't aspire to ever be Git experts. But heavy Git users, I'm guessing, will not be tempted.
GitHub.app seems like it's trying to take some of the complexity out of Git for beginners. For example, I'm looking at the "Changes" tab and don't see a distinction between staged and local changes. There's just a "Sync Branch" at the top that presumably does a pull, you don't get to have multiple remotes, just a "primary remote repository". No --rebase on pull, either.
Basically it looks to me like GitHub.app is trying to make common scenarios a lot easier to understand, but you have to go elsewhere for anything even slightly outside the lines. Could be the right tool for getting Git newbies (or even VCS newbies) onto the Git/GitHub wagon, especially for those who don't aspire to ever be Git experts. But heavy Git users, I'm guessing, will not be tempted.