honestly its all preference. quite honestly most people can make do with a normal sized mousepad.
a larger pad may be nice IF:
- you have your mouse set to low sensitivity and need large amounts of space for things like precision mouse work, art or drawing
- you like stretching out and often change arm positions so a bigger mat means you do not need to shift the pad around when you do this and can just move the mouse (this is why i use a big pad)
- you like the look of a big mat better
- you want a full keyboard and mouse pad either because you like the look or want a softer/washable surface under them both (compare to a desk pad)
my main go to pads are an 11x17 which gets used for the desktop and a normal sized but thick pad which...