I nearly went for a 6 plus when I got my 6 last year, but felt it was just a bit too big. When the S was announced, I decided that I was going to wait out for the 7. However, O2 brought out some really good deals on the 6S and 6S Plus (30GB data, free insurance and a free upgrade after 12 months) so I had another look at the 6S Plus.
This time, I felt the size wasn't so much of an issue (probably because I've been using a 6 for a year) and decided to pull the trigger on a silver 128GB 6S Plus (I was tempted to get a rose gold / pink one but they didn't have any in stock).
After trading in my 6 in store (I got £300, which is less than I could have got on eBay but also a lot less hassle and in line with what other recyclers were offering), the upgrade only cost me £70.
The phone costs £5 a month more than the 6 did and the 30GB (with the free insurance and free upgrade next year) contract £5 a month more than my old 20GB one did so all in all a pretty good deal
I've only had the phone for a few days, but I've not found an issue with the size at all and absolutely love it 😀