I like both mail programs, however, I have to say that after installing Outlook 2015 and messing around with it for a while that I moved my Mail.app account to Outlook 2015. Now, I still have to use Mail.app for some things since you cannot sync calendar, contacts etc..to Outlook 2015, just email.
Outlook 2015 synced everything SUPER fast, and the program itself is very fast and fluid. I have had no problems with it so far.
Do not listen to most of the people on this forum, because most are Apple Fanboys and will ALWAYS say anything from Microsoft is garbage.
People are complaining about how it just looks like the Windows version, and complaining about other stupid little things. I think Microsoft's goal with this release was to improve to code and make under-the-hood improvements, which they clearly did. It is WAY faster than Outlook 2011, very fluid, and I like the interface a lot better than Outlook 2011's. I think Microsoft will add features in the future with updates, and I think A LOT more features will be added when the full suite is released in 2015.
I say try it for yourself, and see if you like it. Outlook is a lot more powerful than Mail ever could dream of being.
