agree - the terrain / type of riding you do is a key factor - as is the condition / level of fitness of the rider

a double with a 34 or 36t small ring might not be ideal for some riders with a lot of climbing (30 or 32 might be more appropriate) ...

cassette also comes into play of course - with a 34t large cog a 34 or 36t small ring might be more agreeable

of course if the riding is primarily flat - just about anything goes ... an old road bike with a 42/23 combo will work - the same bike that will barely get you out of your neighborhood in a hilly area