iPad + external keyboard > any tablet.
Say what you like, iPad still continues to dominate the tablet market by a landslide: apps, experience, you name it. Oh, and sales figures.
iPad + external keyboard = inferior notebook
Say what you like, tablets are still toys with only very few real world use cases. The moment you actually want to DO something, you do what the guy in this (admittedly rather poor) video clip does: You grab for a notebook.
Tablets make nice surf boards for light web browsing (reading, not writing) and eBook and comic book readers. For everything beyond that, any PC notebook which costs less than an iPad but has much more power is a better choice. Even watching videos is a better experience on ANY notebook than it is on a tablet - you don't have to old the damn thing and the notebook also has a bigger screen, which certainly is an advantage when you want to watch a movie.
All that being said, if I really wanted to buy a tablet (or hybrid/convertible) right now, I'd go for a machine with Windows on it, either a Surface or a Transformer Book. The new Baytrail CPUs are awesome and I can confirm from my own experience that the battery of the Asus Transformer Book T100 lasts for 11 hours - even while watching videos. You -can- run any Windows software on it, if you need to and the Metro/Modern UI part works very well on tablets. In other words: This is a tablet AND a REAL machine. The downside for me is the small 10" screen - but I already said that I find tablets mostly useless.
Android would be my second choice for tablets up to 7" displays. It's true, there are still not many compelling tablet applications on the market for Android, so the Nexus 7 is the best Android tablet that money can buy. But in my opinion, 7" to 8" is the perfect tablet size anyway - remember, I said that these things are only good for light web browsing and eBook reading. And eBook reading is a chore on anything larger than 8". I also have an affinity for the Nexus 7 (2013). It's a beautiful, powerful little machine at a very attractive price. It's only downside: You can't use it as a phone. Why would anybody want to carry around two mobile devices when you can have ONE device in your pocket that can serve all those purposes? Enter Galaxy Note, Galaxy Mega, HTC One Max, Huawei Ascend Mate - they're called phablets. Something that you can't buy from Apple.
iOS still only appears on my radar screen as something that has to be avoided at all costs. It's an OS solely designed for the needs of the control freaks in Cupertino and hence it's the only platform out there that does NOT let you have your cake and eat it. It's only there to restrict the abilities of the users, not to empower them. Which is a shame, really: Apple does build beautiful hardware, but only to castrate it with their extremely restricted software.