Quite frankly, I do not notice a significant enough difference between my 8 speed 12-25 and my 10 speed 12-25 on the same double crank. My 9 speed 11-26 is about the same. It's not like you only have a handful of ratios to choose from. I don't know how I ever did my paper route 35 years ago on only five speeds
IMHO, when you start talking about increasing cassette capacity, unless you're going from something like 12-23 to 11-34, it's all about the middle being more compact. I prefer not having to switch gears three times to get to where I am comfortable (10 speed). Would rather have an 8 speed and one, maybe two shifts. As for climbing as it relates to ratios, take what you have and pedal harder/more efficiently. It may seem harder, but your body will get stronger to compensate. You'll never get stronger by making it easier to go up hills.