Samsung has used the framework of the SGS4 (Samsung Galaxy S4) to produce the: -
The Active being the indestructible* version, also waterproof. Size and specification the same. (*not really, but a lot closer than the others!).
The Zoom being a great step forward in direction of camera's. A wise step forward as smart phone users are taking cameras out less and less knowing that they're able to take fairly good snaps with their camera. I for one certainly would head to all socials armed with a compact camera to capture memories from the evening. In my opinion, the Zoom also is a good step towards being able to hold onto your smart phone properly, rather than balancing between a few fingers while taking self-ys, there is a nice big grip and front facing pictures using one hand can now be taken without worrying that the phone is going to slip and fall to its death.
Lastly the Mini. As I mentioned to start with the SGS4 is a great phone bar one feature in my opinion, it's too big! Don't get me wrong, I'm not keen on technology being so small that it's barely useable, but technology is not meant to get bigger in such a fashion that it impedes us, doesn't fit in our pockets comfortably, require two hands when they used to be fully operable with one hand and so on. The SGS4 Mini gets round this... to a degree...
So the SGS4 Mini is reduced to a dual core processor, obviously has a smaller screen with a reduced resolution, the FM Radio left out, touchWiz and a few other features rained in.
Other features removed are the split screen options which is a software change and not due to reduction in processor power as the SGS3 has a similar spec'ed processor and split screens very well. The removal of the indicator light. Some people hated it anyway, some people (myself) live by it as a power saving option, by not needing to power on the whole screen to check waiting notifications, but simply able to see what colour(s) the indicator light is flashing, which is also a lot quicker.
Second to last comment, dual sim on the 4G version of the SGS4 Mini would have been nice and tipped the balance enough for me to purchase.
And my last comment is that HTC have lost me as long as the battery isn't changeable (and SD card). They have assumed they know how we/I work and taken away the flexibility just like Apple did. The whole point of Android is that we like the adaptability and flexibility of our phones, please don't restrict them!