I'm in exactly the same situation here. I have a 6+ since February and now I'm thinking about upgrading to a 6S. I've also been wondering which was the perfect combination for me (smartphone+tablet or phablet). I'm still undecided but I think I'll go for a 6S + iPad Air (old but still good) and wait for an upgraded Air in the future. Maybe someone here can help me in my decision. First all, I tried to understand what's most important for me between battery life, dimensions as well as other factors.
Dimension - for me it's fundamental. Since I got my 6+ I always used it one-handed. That's my habit and I'm just comfortable in using smartphones with one hand, maybe because I usually check things while I'm doing other stuff (e.g. checking the bus schedule while holding the shopping bags, etc). My hands are normal and I usually struggle in handling the 6+ with one hand only. It slipped few times. It's also uncomfortable having the 6+ in my front pocket of my jeans every time I sit or if I wear shorts or bermuda, I have the feeling it could slip off easily.
Battery - that is a really important thing for me, but I've different expectations now and I explain why. I've had only the iPhone 4S before so, when I bought the 6+, battery was my first concern. But after 8 months with the 6+ I realized that maybe the 6S could suit my habit.
I consider myself a moderate user. I've optimized my 6+ settings: 3G, WiFi and BT always on. Auto brightness on. Handsoff on. Background app refresh off. 1 mail in push and another fetch every hour. Location services off except for 3-4 apps: weather, maps, transit app and messages as I share my location sometimes. I use my 6+ while commuting and sometimes at night. 3 hours of music (only local, not streaming, over bluetooth earbuds), checking facebook and linkedin, 1 hour of surfing on safari or some travel app with locations off, few minutes to check maps or transit apps. During the rest of the day I use it mostly to check and reply emails, messages or whatsapp. No video or videogames as I use my iPad for that.
I end up a typical day of use with 70%-60% of battery. Recharging my smartphone every night is not a problem for me. Recharging it at 3 or 4pm, as I did with my 4S, is. I'm now trying to gather some information about iPhone 6 (or 6S) battery life. If it can end my typical day with 20-30% I will switch. Can anyone advice me about iPhone 6's battery life? What should I expect with my usage?
All in one device - I tried to use my 6+ as my only device, but for me it's not possible. I use a laptop at work for heavy tasks. I also have a personal blog, and iP 6+ display, even if it's big, it's not big enough to write long posts. I tried one and ended up making too many errors and always switched to my iPad with an external keyboard. I never used my iPhone 6+ in landscape mode to write email or messages, it's just most natural for me the portrait mode. I've also found the auto rotation a bit annoying so I disabled it.
That's it. After analyzing my user behavior I think that a smaller iPhone would be a better fit for me.
Has anyone have some suggestion about iPhone 6 battery life with an usage similar to mine?
P.S.
Apologies any error, I'm not a native english speaker.