Last year I made the decision to switch to the iPhone 7 Plus. This phone is huge. To say it can be used one handed is a bit of an exaggeration.

All of my phones prior were smaller and easier to carry around. 

Below are my pros/cons of owning a bigger screen size and what will influence my future buying decisions. Please note that these reasons are based on how I use the phone. I realize that for other people the list will be different.

Pros

• Watching video – It's easier to watch video and get a bit more immersed in what you're viewing. This is especially the case since I always watch video (unless it's portrait shot) in landscape. 
• Taking photos – This is the biggest benefit for me. I LOVE portrait mode. It's the number one reason I decided to go with the bigger phone. 
• Texting – This one is almost a tossup again. For texting I have to use two hands, and because I do my texts are much faster. However there are situations where I'd prefer to be able to use one hand (running for instance) but can't do that easily. It really just depends on how you use the phone. Since texting IS really nice with two hands I'll call it a benefit.

Cons

• Reading books – On the one hand I like the bigger 5.5" screen as I can more comfortably read through words on the page. On the other hand a smaller screen is easier to hold one handed. If I really want to read a book for longer periods I can pull up my Kindle Paperwhite, or you know.. read a book. I'm calling this one a con since the portability of the phone (smaller is better) outweighs the extra real estate for reading. 
• Listening to books – Almost all of my "reading" is through Audible. Smaller phone will always win here. 
• Running – Yeah, smaller is always better here. 
• Playing games – This is a very low priority for me, so smaller is still better. 

Lately I've been trying to experiment with ways to become less reliant on my phone. I'd like it to be more of a utility than an always on, always available, always in use device. 

The main reason I stick with a larger iPhone is for the portrait mode. I love it! If the next iPhone has portrait mode on the smaller size then it will be an easy decision.

So here's to looking forward to seeing what comes up next!