Personally I prefer "log in" to "sign in" because it makes it stand out more from "sign up", thus hopefully leading to fewer users accidentally selecting one when they wanted the other. And regarding the variations, I've always been under the impression that "log in" is the act of logging in, while "login" is either the situation/event ("a login happened") or an alternative term for username.
You're right that "log in" is more distinct from "sign up" (and works because "logging up" doesn't make much sense), and I definitely agree with you that 'login' is a noun, if anything!
Both "log in" and "sign in" are anachronisms though - they're justified when you're actually signing-in-and-out of a computer system or building to log your visit, but the metaphor doesn't technically make as much sense when you're talking about authenticating the user on a website.
The evolution of the terms does let you nicely abstract away the actual mechanism of authentication for a user, which I suppose is the point.
Re:The origin of “log in” (2011)
by userbinator on Tuesday April 29, 2014 @08:54PM
(#7670936)
> to log your visit
That is what many systems will do when you "log in", so to me that makes the most sense.
Re:The origin of “log in” (2011)
by xentronium on Tuesday April 29, 2014 @06:12PM
(#7670262)
Actually, some people like consistency of sign up / sign in / sign out actions.
Re:The origin of “log in” (2011)
by jodrellblank on Tuesday April 29, 2014 @07:09PM
(#7670534)
I mostly get hung up on "why doesn't this stupid software support Single Sign On, it's 2014, why am I typing my current credentials into a web page that's either running on the same computer, or running on the local network, which is also going to inappropriately lock or kick me out after NN minutes of inactivity".
Touché
Re:The origin of “log in” (2011)
by rowyourboat on Wednesday April 30, 2014 @04:51AM
(#7672214)
As a non-native English speaker, I prefer “log in” to “sign in” as “sign in” is very similar to “sign up” which some sites use instead of “register”. The difference between “sign in” and “sign up” is subtle and requires me to consciously think.
Use "log in" and "register". Don't make me think.
Re:The origin of “log in” (2011)
by billmalarky on Tuesday April 29, 2014 @07:00PM
(#7670491)
I have the same struggle. I'm actually glad I read this since now I can just go with "sign in" and know that it is at least objectively the most used and therefore likely to be most understood by users.
Re:The origin of “log in” (2011)
by johnchristopher on Tuesday April 29, 2014 @06:14PM
(#7670271)
Would "connect" work too ?
"Authenticate" might be the most correct verb, although it's not very user friendly?