What do I base my selection on?
They were cheap!
They were also plain ... as in no advertizing. If I want to go around looking like a billboard for some large sports company, that sports company had better be paying me to wear their jersey!
They had the look or feel I was after - comfortable, nice cut, a variety of colors ... plus some are sleeveless for hot days, some are short-sleeved for average days, and some are long-sleeved for cool days.
And I do have three that are Canadian - two for teams I've been on, and one that is just a Canadian jersey. I wear them when I participate in international events.