Upgrade from iPhone 6+ to 6s?

So I've had my iPhone 6 Plus for 1 year and 1 month and yet I still haven't got used to the 6+, my dad got me the phone and it's really irritating me from how big it is, I called the place where my dad got the phone and they said I can replace it for a fee which I can pay off myself, my dad said yes and everything but I'm scared there will be a dramatic difference to the phone since I just at the largest phone in the world, I think it will be hard to get used to the normal 6s… Will it?

Keep your old phone until the time you really find a feature in the new model not found in your old phone and you need that.

Thats a good upgrade