I've been giving some thought to gear ratios lately, having had my son's Ricci road bike upgraded (see previous post). There are plenty of gear tables online, but they don't really give a good visual image of how much overlap there is between chainwheel gears to help decide when you should change chainwheel, or to compare different bikes and planned changes. So I've produced my own, based on a standard spreadsheet where ratio = chainwheel / cassette sprockets. (My wheel sizes are all the same, athough my hybrid has bigger tyres.)
Surprisingly my hybrid bike has higher as well as lower gears than my road bike, due to it's small 11 cog. On all bikes it makes sense to change chainwheel after 3rd gear - although on both bikes I tend to stay in my middle chainwheel most of the time.