I am retired, so weekends week days, all the same to me.I prefer weekdays because in addition to having less people playing, the level of players is much better.
I'd say it depends on what you're looking for. If you want big guaranteed prize pools, like the Sunday Storm on Stars you have to play weekends, especially during series like WCOOP. If you can play during what would be the day time in North America on weekdays the prize pools usually aren't bad, but if you're playing in the evenings you're probably playing against a smaller player pool and might even struggle to find games at a specific buy-in on smaller clients.I prefer weekdays because in addition to having less people playing, the level of players is much better.