Wow, tough choice. I think I like the toe of the second pair for sure, a lot better. But I kind of like the slouchy-ness of the first pair... overall though, I would go for the second pair. Hope that helps; and sorry but I can't offer any help on the sizing, I haven't gotten shoes from them before.
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"In matters of grave importance, style, not sincerity, is the vital thing"
I like the first pair better. I would get the 6 just because they're boots and you will probably wear heavier socks or whatever with them, and I'd rather my boots be a little looser than super tight.
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Fashion your life as a garland of beautiful deeds. -Buddha