I think a canvas bag can be formal such as the eva, the alma bb without the strap, the favorite and I think the PM can be if used without the strap. I just used my bag at a formal LV event and I think it looked just fine. I also find it to be a nice casual bag, it's all about how you style it.
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The difference to me between this and Eva is the chain. I think the chain adds a touch of formality to the Eva that the PM doesn't have. Yours is slightly dressier because it's blank.