You should care, the console with the larger install base, ease of programming and higher ceiling is more likely to have the initial code written for it and the weaker/smaller base harder to program console then gets the crappy port.
This was especially true in the early days of PS3. the PS3 had a small install base due to the early launch of 360 and was difficult to program for. Most cross platform games were ported to PS3 and they are laggy, sloppy, jagged glitched messes.
Bottom line is if most of the other people buy the PS4 then the product quality of the xbone will suffer.
That is one reason why you should care about other peoples purchasing trends, amongst quite a few others.
The reasons for being in favor for either console are readily available and discussed quite a bit.