About the only differences you'll find are features. I wouldn't like to give up my S-Pen, for example, but some people never use it. I won't buy a phone that I can't remove the battery on by popping off the back cover.
If Motorola had the same quality it had back about 10 years ago, I wouldn't buy anything else - but, sadly, they left quality back about 10 years ago and haven't been able to find it. (I mean like my StarTec slipping out of my hand in the rain, dropping 3 feet to the blacktop, skating about 100 feet across a sheet of water and ending up with a scar on the back of the case you can't find unless you know where it is. (The phone still works, even though, since it has no GPS, it can't be activated.) I still use my 10 year old V551 as a backup phone. If it gets "lost" or damaged, it'll cost about $20 to replace - but it has a more sensitive receiver than almost anything on the market today.
But now? About the only advantage of Nexus is the price. You can get the same quality phone for a lot less than the other manufacturers. But the phone has to be opened to replace the battery.
I want an HTC with an S-Pen and a replaceable battery. (And a check for a million dollars, while I'm wishing for impossible things.) So my Note 3 stays as it is until it dies. (Or until someone comes up with a way to root Lollipop on the AT&T version, at which time I'll update.) My next phone? We'll see what's there when the Note 3 dies.
As for your choice, any Samsung phone on Verizon (or AT&T) will have a locked bootloader (and Knox), so flashing a different kernel is impossible, and any ROM will have to be a variation on the stock (bloatware removed, rooted, etc.) if any of that matters to you. About all I've seen that might be better than the other 1Q 2015 phones is the 64 bit processor. That will do more to future-proof it than anything else (assuming it has a lot of RAM and internal app storage).
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