I use a combo of both and it depends on what I'll be doing and how long I'll be gone for.
A pillow case is perfect for traveling where the snake won't be moved much aside during transport and for examination. But when I go to my parent's for the day, I bring a tote and pillowcase. I use the pillowcase for the travelling and put inside the tote. When I'm at my folks after my snake has had enough fresh air, I put the snake in the tote with a water dish and then cover it with the pillow case so it doesn't get stressed. That way he can move and drink if he wants and not be too restrained for long.
Keeper of 5 snakes, leopard geckos, 1 green iguana, 20+ tarantulas, 2 dogs & a bunch of rats!