Now, before I go on, in the interest of not filling this article with assorted exceptions for perfect accuracy which I could never possibly achieve anyway, kindly allow me to make the general point bearing in mind that, as usual, what I write is only approximately correct.
Hardly any customers actually care about space. My mom is definately in the “I don't care” camp and I bet your mom is too. Never once has she called me and complained that “Word is too big”. So, my friends, it turns out speed is everything.
But wait, why then do I devote all this attention to measuring space, whole articles in fact, if nobody cares? Well, the reason is that as often as not space is speed. Yup you heard it here first folks, all that stuff they taught you about time-space tradeoffs is bunk: your default assumption should be that smaller is faster. Which is why we pay so much attention to space, because often the primary cause of slowness turns out to be bigness. Whether it's page faults, cache misses, or just tons of IO, space kills.
I love my mom, but she wouldn't know a soft-fault if it hit her on the head. She just knows it's too slow.