My 2 cents. I primarily use my rmbp for all my computing needs and it works flawlessly. I do have an occasional need for windows to program home theater remotes and did rely on bootcamp which increasingly became unreliable with usb ports. Recently I purchased a surface pro 4 and a surface book to evaluate. They both are nice machines but I felt the surface pro 4 did not live up to its battery life claims of 9 hrs. I was lucky to get 4.5 to 5.5 hrs. The surface book got great battery life except when in clipboard mode which was 3ish hours. I am really wanting to use one note for lots of note taking and marking on blueprints. I felt that I wanted to use the tablet mode more for note taking so I thought sp4 would be the ticket but the battery life like I stated seemed like it couldn't make it through a work day. Surface book's battery can make it through a work day but is 3.2 lbs which is too heavy to carry around for notes. So I returned both surface units and got a ipad pro and an open box yoga 3 pro for my occasional windows needs. The ipad pro is a great device but... one note is lacking compared to the surface version. I am currently testing notability for ios but it is also lacking in features. The beauty of one note is it's syncing ability and access from many devices and the onenote website. I would hate to be locked out of my notes in case of a device failure. Tonight I feel like after all of the device evaluations the Surface book remains the top device on my list for note taking and serving my windows needs. What is not so great about windows 10 is the lousy mail app, touch interface doesn't work properly on all websites, and high resolution scaling issues with some programs. If I go back to the surface book I will mainly leave clipboard detached and charge it in the car between jobsites with an inverter and have the keyboard base as a battery backup and for computer mode. One thing I have also noticed while using the ipad pro is back and neck pain. There is no kickstand or base to attach it to while sitting on the couch. The ipad pro is a big tablet to hold up so you end up sitting it in your lap with you neck bent over looking at it. If the yoga 3 pro had stylus input I could live with the terrible trackpad. Decisions!!!
Totally agree about the Windows 10 mail app. It's not full featured, and if you are using gmail, flags don't sync and when you delete something on either the app or the gmail webpage, it takes hours to sync either way. It's flawed and many people are complaining. The other option is to use Outlook 2016, which is clunky, has way too many features, and as of now does not use oauth 2, so if you want to use it with gmail, you have to go to your gmail account and either get an app specific password or actually select to decrease security by opting for 'allow applications with low security to access gmail'. Oh, and Outlook 2016 does not offer gmail calender or contact sync at the moment. You can only view your calendar but it won't allow you to make modifications from the app. So basically MS on BOTH their main email apps, offer incomplete products -- for gmail access anyway. OSX's email app is great and it uses oauth 2 (the small google log in screen when you enter your account info during setup). The sync with the google server and the osx email app is also instant. By the way, windows 10 also does not offer any PDF editing software. Just rinky-kink app called "preview" which opens pdf's but that's it. Can't rearrange, modify, sign... nothing. OSX's preview allow for full PDF management. It may sound silly, but I switched from my long trusted and used windows desktop computer (i7, 16 gigs ram, 1 terobyte HDD + 256 SSD, dedicated ATI graphics, top of the line Japanese made gigabyte motherboard, running windows 10... to a fully loaded iMac. I was so disgusted by MS offering totally incomplete stock software. I don't want to download Thunderbird (which is no longer supported) and all other 3rd party email apps seem to be a sercurty risk as NONE support oauth 2. With 4 gmail accounts, I'm not about to access all my email from a web-broswer and need a full featured email/calendar app. Anyhow, that's my take on email.
As far as OneNote and surface vs ipad pro... quick question, what are the features on OneNote that make it that much better than the Notes app on osx? You can draw with a pen on the notes app on an ipad and it syncs across all devices almost instantly. It is also web accessible via any browser. You can also regularly back up your osx notes by copying a file in the directory and keeping it safe somewhere.
Agreed with MS hardware... battery life is usually not what is stated.