Thanks everyone...
Did a quick tour today and here's a quick summary for future reference.... (I won't provide L\A\S numbers as it's so subjective LOL)
Watts - rental only so didn't go there. Would likely be good if you're looking for higher end well made costumes
More Madness - really helpful lady. You need her help because the store is literally overflowing with stuff piled in there. Fairly good selection of complete costumes and accessories. The prices are high but she discounts readily.
Party Bazaar - not just costumes but full party needs, even for kids. Smaller selection of complete costumes but the prices are better than More Madness even after the discount. Would be a good place to start at and then head over to MM if you couldn't find what you want.
Boolala - (North Van), about a 50% mix of rentals and sales. Hard to characterize the place but if I had to summarize it they had a wide selection of nothing from the sales perspective so perhaps more appropriate if you want to rent. Rentals were actually pretty reasonably priced (IMO) - say $100 for a gangster outfit, much higher quality that you'd be able to buy...
Cheers