Best 20A IEC power cord

So I take it that for most power cords, a simple switch from a 15 amp to a 20 amp IEC connector would do it? (Of course, even 15 amps is a lot of wattage so I wonder how often the cord would be called upon to deliver more) Are there any other design parameters that need to be considered with a larger end plug and a potentially higher current drain? Does the 20 vs 15 amp provide more current "headroom" only if the cord is designed for it? (I'm blindly borrowing a term from a different context here)

Thanks for all the comments so far.