Whatever I speak is from user experience. I own an android phone myself. My roommate owned a Samsung Galaxy S5 while another owned an iPhone 5S. Also, there may be times when I'd go into specific models or even generalize. The topic is sort of weird so forgive me if there are instances you notice when I'm not exactly going with "Samsung vs Apple" and concentrating on, say, "Android vs iOS" or "S6 vs 6".
Pros with Apple phones:
Elegant design (subjective but generally better than Samsung mobiles. S6 is an exception to the rule, though)
iOS generally doesn't lag. Also, way lesser crashes.
Simpler UI for a daily smartphone user. Lack of complex features and settings make it difficult to do something accidentally so you mess your phone up.
Better service, generally.
The updates. All devices get updated as soon as a new version of the OS is out.
The cameras they use are top-notch. Industry-leading standards. Other companies usually play catch up. 6S will definitely dominate S6's camera when it releases.
Pros with Samsung phones: (talking about flagships since only the flagships actually compare performance-wise with the iPhones)
With android, you're much more free. Can do a lot more than with iOS.
True multi-tasking. iOS doesn't allow that.
Customization possibilities are literally endless. You can ACTUALLY make the device your own.
You can tinker with your system a lot more possibly allowing being able to get more out of your device than it usually can deliver.
Also, Samsung phones generally last longer on a daily basis. S5 had a better a better battery life than my other friend's 5S.
Their SAMOLED screens are top-notch and offer infinite contrast ratio by switching off individual pixels when not in use. Colors POP out much more and look attractive.
Some of the points in Samsung's favor are actually more true for android devices in general.
Now, some cons for both. Both mostly deal breakers for me:
Apple - Lack of freedom, Pricey.
Samsung - Touchwiz, even with its stripped down lollipop version, still lags.
Another issue I have is, well, there's their butt-ugly design for most phones that are not S6. S6, although good looking, is pricey. As expensive as iPhones. So another no for me. :p
Overall, I consider them about equal. Not an especially big fan of either. I like iPhones because they look sexy. But their lack of freedoom is just too much for me to overlook. As for Samsung, TouchWiz spells doom for it. With a custom ROM, though, most problems would be solved. I'd love to have an S6 running some great custom ROM like exodus that I'm running on my OnePlus One. Now that'd be a great phone to have. :p
But installing a custom ROM = tinkering with the product. With the product as it is - as it is given to me, I'm not a fan of it. If we're comparing them, I'd compare them without going with modifications made to the product via the user like installation of custom ROMs and stuff. Besides, most users don't do stuff like that since they're usually more concerned with not getting into possibly system-breaking processes and prefer to use phones without messing around with 'em. In that regard, for me, right now, an S6 = an iPhone 6. Both have their pros. But they both have issues. Same goes for both the companies in general.
