iPhone 6 or 6 Plus?

Hi.
It all depends on what you want. If you want a bigger battery, then go for the 6 plus, like you said, having a bigger screen will make it easier to type, not necessarily faster. That all depends on your typing speed on older phones. If you typed fast on the 5S then you should be able to type fast on the 6 plus. If your friend has a 5S, then if he wants to stay at iOs 7.2 or whatever the last release of iOS 7 was, then good. it's his choice. I'm waiting till next year when they release a new phone again and upgrade in september or october of next year.
If I were upgrading now, I'd go with the top 6 plus, 128GB of storage, color doesn't matter, space grey like my 5S is now. I have a 5S 64 GB. If you upgrade, do not buy a 16 GB. If you do, the size of the free space is 12 GB, so no point in upgrading to 16GB devices anymore. Sorry if that sounds negative, but that's just my opinion!
HTH and have a great day.

I'd also opt for the 6 plus for the bigger battery. Battery life is everything to me as I am always on the go.

Hi,
I bought the Iphone 6, but in some ways, wish I had spent the extra money and purchased the 6 plus. My logic behind buying the 6 was that this is my first Iphone and I wasn't sure how I would adjust.

What is the size difference between the 6 and 6+?

i got the 6. i was initially very upset about how bad the battery life was being my first i phone i had nothing to compare too. since the last two updates its not as bad. Still not great as i'd have prefered and hoped it would be but its slightly better. The 6 is pretty big no idea how big the 6 plus is as the 6 is not exactly small very thin but pretty widea nd tall

iPhone six plus is 5.5 inches, iPhone six is 5 inches.

Yes, so it is. I stand corrected.