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I wouldn’t cancel either of them, I would apply for Discover if it was me.
I am curious about your stats though, $300->$500 is low for a well-managed credit steps card in my experience. The fact you aren’t prequalified for anything else raises questions too.
680-700 is FICO or are you looking at CreditWise/Credit Karma/etc? Income, any late payments, how many inquiries, etc?