Which smartphone to choose? (iPhone 5S vs HTC One)?

I have an HTC One at the moment, and I'm quite bored of the Sense UI. I'm willing to change my phone. I'm considering the Apple iPhone 5S and the LG Google Nexus 5 which is going to be offered in November 1st hopefully. And I don't really know even if it's a good idea to trade my HTC One for either of these great phones.
I'm mostly considering the iPhone 5S because I think it's good to make a change and migrate from android to iOS. But the BIG problem is, I have an iPad mini running iOS 7.0.3, and I wanted to know if I'm going to experience a redundant UI on my phone and tablet if I purchase an iPhone 5S. You know, having an iPhone and an iPad I mean. Some folks believe it's good to have a good android phone and an iPad so you'd have the best of both worlds. But some say iOS and iCloud features and stuff are designed the way you never miss anything android-ish while you own an iPhone and iPad and you're going to be perfectly fine. I don't know whether these statements are true or not.
Plus, I have done a research on specs of HTC One vs. The iPhone 5S and I concluded that the hardware specs of the HTC One are Way better than the iPhone 5S'. For example:

Battery Capacity --> HTC One: 2300 mAh / iPhone 5S: 1570 mAh
CPU specs --> HTC One: quad-core 1.7 GHz / iPhone 5S: 64-bit dual-core 1.3 GHz
RAM amount --> HTC One: 2 GB / iPhone 5S: 1 GB

And tons of other stuff!

And there's the android vs.iOS thing again. You know it all, android is more customizable, tinkerable and you can download unverified.apk files from anywhere you like; unlike iOS in which you are only allowed to download certified apps from the Apple Appstore. And there's another thing whose lack of existence in iOS bugs me A LOT and that's file sharing via Bluetooth, NFC, Wi-Fi direct and tons of other connectivity functions which android supports and iOS doesn't.

Another factor is the display screen size. I really have NO idea what size of a screen I need. Some people say 4" is too small, some say 4.7" is too big. I believe 4.7" of the HTC One is a little big and thus uncomfortable but I don't know whether a 4" screen size is enough or not.

In conclusion, considering All these factors, which OS and which phone is more suitable for me and my lifestyle?

I hate apple. Too simple. The only thing they have over androids really is that they get updates/certain apps quicker really. I have the LG Optimus 9 and I loves it so much <3 samsung galaxy s5 is supposedly coming out next year as well: D

I think specs will be the least of your problems. As far as I could see iphones Doesn't experience bad lag with multitasking compared to androids with the same specs probably because of the widgets. But if you're just bored with how your phone looks you can always try a launcher I know that's what I do. I have nova, buzz, themer and currently I'm using aviate. That alone will change how your phone looks. And if you're bored with sense I wouldn't suggest going with iPhone because it'll be a matter of time Before you get bored with it because you can't do anything with it. I suggest getting some of those launchers I just mentioned while you're waiting for the release of the n5

Yes, on paper the One is better than the 5s, but in practice where it actually matters, its not.

http://www.anandtech.com/show/7335/the-iphone-5s-review/5 will show this.

Apple does have the ecosystem thing down. Apps can work between the 2 devices & work in sync to make life easier in most aspects.

Technically the iPhone 5s can now share via bluetooth, though its disguised as AirDrop.

Try an iPhone 5s at a store to see if the size is good for you or not.

Oh & you'd end up with a much more capable camera.