Should I buy the Mi3 or iPhone 5/5s or iPhone 6?

Currently using a 3Gs but have an iPad mini, I'm currently debating on buying a new phone. I stumbled upon Mi3 which is a bang for buck phone and top of the line specs problem is brand-wise (Chinese, Xiaomi) and it's Android which means having to learn a new ecosystem. Now enter iPhone 6. I've been wanting a larger display for a phone now but it's too expensive so I'm thinking about 5/5s which is still a decent uprgade. Should I buy the Mi3, 5/5s or wait til 6 gets cheaper?

There's the Mi4 out now too, and that is utterly amazing for the price. 1080p full HD 5" LCD display, 3 GB RAM, 13mp rear camera and 8mp front cam, shoots 2160p video @ 30fps, SnapDragon 801 at 2.5 GHz, Adreno 330, dedicated noise cancellation mic, 3080 mAh battery, just killer specs. All for $450 off contract.
If you're used to iOS, Xiaomi's tweaked version of Android is pretty similar to it, in that there are icons in pages in the format of iOS, but there's a separate dedicated page (which you can add on to) for widgets to optimize widget size and ratio with screen orientation. (The dedicated widgets page is true on the MiPad, but I'm not sure whether that translates to the Mi4, but the overall look is similar to iOS nevertheless)
Sure the iPhone is good, but it is extremely expensive and some of its features are catching up to older phones like the Nexus 4. I think iPhone is way overrated in my opinion, especially for its rediculous pricing (128gb iPhone 6 Plus for $950!) and the Mi4 will surely make you stand out. You'll just have to check with compatibility with mobile services depending on where you live.
Another thing is if you are on Verizon or buy an unlocked one (if you live in the US) or if you live in Europe or elsewhere, you can get a Nokia Lumia Icon/930. 20mp PureView camera and otherwise similar specs to the Mi4 (but 2gb ram instead of 3gb). If you like Windows Phone 8.1 and don't mind too much about the app gap, then that is one of the best phones for its money, around $500 so you can check that out as wel

Sorry for the long answer but I tried to provide the information and help that I could, and it turned into a longer answer than I'd hoped

As Abhinav said, the MI4 is an amazing phone for the price… Apple products in general are overrated and overpriced but the only reason they are so popular is apple fanboys. For them, anything that is made by Apple is better than… Anything.