I am looking to get a new phone next year. I have been considering Samsung in the past due to how popular their Galaxy devices are compared to other Androids. I have seen more Samsung Galaxy devices than other Androids personally. I own a Nexus 5 currently. It already has the Android 5.1 and I really like the stock Android feel and performance. The Galaxy S6 and S6 Edge are already out, but I will not be able to upgrade until next year. What would be sacrificed after switching from a Nexus phone to a Samsung Galaxy phone? I have also never owned an iPhone, but use an iPad Air from time to time.
The difference in the look - "stock Android feel" - is in the launcher, and you can replace the Samsung TouchWiz launcher (which I personally can't stand) with one closer to stock Android, or any other launcher - Nova, Holo, Apex, Go ... whatever you want. It's just an app.
Unlike most other manufacturers, Samsung still has phones with external SD cards and removable batteries, two of my "musts", but they may not matter to you. I've had great Samsungs, and some that had to be replaced almost out of the box. I've also seen the same situation with most of the larger manufacturers. So is Samsung better or worse than any other phone? As a general rule, no. You can get a dud from any manufacturer or you can get a phone that will outlive you. (My Motorola V-551, one of the first phones to have a camera, is still running fine. Even my old MicroTACs would be running fine - it they could be used today, but we don't have any analog cellphone signals any more.) I have old LGs that still work too.
Look at the features (assuming you've researched which carrier covers the places you need service) and decide on that basis. (About all you "sacrifice" when going from a Nexus to an equivalent Samsung is money - a Nexus is always going to be cheaper.)
.... although by spring 2016, Apple will have invaded South Korea to capture all the best minds working on new ideas at Samsung, - with the private army they are training as we speak (look in your local jobs newspaper "Do you want to kill in IT?") - to help fast forward their one new phone idea pertaining to moving screen tiles (codenamed 'windows' - shhh! ) to restore confidence in a lot of their followers who are starting to not fully accept the stock responses of Store Geniuses to the thought that: "wasn't all this stuff in last year's phone, and the year before that?".
One remaining bright spark at Apple had suggested to maybe hijack the best Google brains instead, to save on transport costs, ship and aircraft acquisition, and translators - but as Siri and Apple Maps didn't know where Google were, Seoul is now a go!
IOW, a year is a long time in 'telephony' 😆.
You could probably then be asking is Xiaomi starting to lose it's stranglehold on the premium market to Huawei because their phones don't roll up into a ball.
Who knows if Touchwiz will exist, or if Nexi will be full of bloatware.