I am going to assume in your first sentence you meant to say the iPhone 6S PLUS is quite a bit larger than any Samsung phone... which I pretty much agree. But I don't want an iPhone 6 Plus sized phone... I really dislike the 6S Plus dimensions.
That's why I was ok with the Note 7 being a size at my very limit of preference. I am more ok with the 7 Edge and S7 because I also feel the regular 6S a bit too small and wish they went up to S7 size...
I am ok with S8 rumored dimensions... I will have to be since it will now be their smallest S phone... but they are getting bigger and bigger every year to the point if they don't stop they will size themselves out of the market for people like me.
I wanted a Note 7 but they messed it up and can't get one. If the trend of the Notes being larger than the S Edge phones then that thing will just be too gianormous for me.
With your dimensions listed above, please compare Plus to Plus... the S8 Plus will now be wider than the iPhone 6S Plus (shorter but little thicker). No thank you then. Again, imagine if the Note does follow trend and is bigger than the S8 Plus... Too wide for my preference.
The iPhone 6S is quite a bit larger than any Samsung phone. I have no issues with the size of my 5.7" Note 5.
Here are the dimensions for the 5.5" iPhone 6S Plus.
158.2 x 77.9 x 7.30
Here are the rumored dimensions of the 5.7"
Galaxy S8.
140.14 x 72.20 x 7.30
That is much smaller than the iPhone 6S Plus.I don't really see the problem with putting the phone in a pocket or in an armband.