You can use something like this
http://www.gsmarena.com/compare.php3...&idPhone2=7995
Most Android mid rangers now will have as good or better chip than the S5, with a better graphics chip, more RAM, and a bigger battery, and Marshmallow upwards is significantly better than Lollipop (presumably the S5 still runs that) in performance and power usage. But for what you need it could be worth getting another year from the S5 with a reset.
The iPhone is also worth a look if you can get an SE or 6 upwards at a decent price. Again, from what you've said you want then iOS will be perfectly fine.