uh...the Mini won't be that much better in the winter...
generally I'd go for the e46, mostly because both cars are about the same price, but with the Mini you'll have (like notallthere said) a big loss when selling it again. Of course the Mini will be a bit cheaper in maintenance and stuff like that (also it's under warranty). But since you haven't really told us which engine the Mini is supposed to have (Mini One, Mini Cooper, Mini Cooper S, Mini Cooper Works) the comparison is kinda hard...