I love both...especially the red halfmoon. They both look great on you and I don't think it looks too small for you height. I have a dark red woc and It matches with almost anything. I'd say keep the red because it's a more versatile and a great pop of color for such a small bag, more so than navy blue. I'd rather get a bigger bag in a black. For a small purse red is perfect.
LOVE the pop of color of the red with your tee and jeans!!! So cute! I think in these clothes, the black does look a bit small. I mean totally fine, but it is quite small so if *you* don't prefer the way such 'micro' bags look, maybe not ideal. I also prefer the way the half moon sort of molds to your body more. I think they're both fabulous but if you wear lots of black and neutrals, the red is amazing!