Isn't it obvious. I mean you can make a program using 100kb space, but if it can produce same result in 80kb then its better as it saves space. Using the same thing you can say if a solution can provide the result in 80ms than a solution which generates the result in 100ms, the first one is better. We always want to save space and time, as both of them cost a lot...😉. I think a programmer should try to minimize both of them.
I guess the main question is how to prioritize them, sometime a better time complexity needs more space. Now its tough decide where to compromise.