Sign In. Like you, I was ambivalent. I went with Login. Surprisingly, a couple friends, who don't take a particular interest in tech stuff, mentioned to me that

Sign In. Like you, I was ambivalent. I went with Login. Surprisingly, a couple friends, who don't take a particular interest in tech stuff, mentioned to me that they'd prefer Sign In, so I switched it. I still don't think it matters much.