What is tougher to run, miles or kilometers?

xfit is tougher.

3 miles is longer than 3 kilometers.

that's an easy question...

Interesting psychological question. Personally I like to think of the start of a hard workout or race in miles (only 6 miles today) and the end in kilometers (just finish up this k/make my move in the next k).

I don't know if this is what you meant to ask about, but I would be interested to hear if others feel the same about this.

Kilometers are easier because they're are downhill.

I split long races up into 5Ks and think about those splits. Much easier than miles.

km are easier to run because they go by quicker.

For instance, is it easier to save 5 dollars or 20?