@chaley,
I've sent the debug log from my Android alter-ego id. I also include here a link to
4 screenshots of Book Details of the same book. Actual calibre cover size 669x1024.
Galaxy Note3 (1080x1920) portrait - BD cover size Medium - actual size 31x47mm of total screen size 71x125mm
Galaxy Note3 (1080x1920) portrait - BD cover size Large - actual size 41x63mm of total screen size 71x125mm
Galaxy TabPRO 8.4 (1600x2560) portrait - cover size Large - actual size 29x45mm of total screen size 113x180mm
Galaxy TabPRO 8.4 (1600x2560) landscape - cover size Large - actual size 29x45mm of total screen size 180x113mm
I'm not sure of the right approach either

merely food for thought. If it's a choice between a smaller sharper image or a bigger fuzzier image I
think I'd choose the former, but as usual with these things, it's not until you've tried both that the personal 'winner' emerges.
So far I've been using CC in portrait on the tablet. Not necessarily because it's better but because it 'feels right' because I'm so used to CC on the phone.