Personally, I went with the G Watch, but it was by a small margin. The larger battery on the G watch and a disdain for samsung's business practices (I fear samsung will be more likely to lock down the OS and/or design apps specifically for use with Samsung phones - although so far it seems like Google is doing a good job keeping things uniform across devices) were two of the deciding factors. I would have preferred an AMOLED screen and higher resolution, but the screen isn't *that* much better than the G watch's screen.
I think the gear live is the better choice if you intend to have the screen always on, especially with a mostly black background (power saving with amoled), and plan to use it primarily as a stylish watch. The gear live is subjectively better looking, and a nice watch face that's always on could potentially make it look even more stylish. The battery is sufficient for a day's use of a good-looking watch that you occasionally use for google now and other apps.
However, if you turn off the display's "always on" feature, and plan to use the watch extensively for apps/google services, I think the G watch delivers better battery life. So far, I haven't minded tapping the screen to see the date and time, so the watch display is almost always off - meaning the battery savings with samsung's amoled display would be nearly negligible for my use. However, I'm using the watch a LOT: I use it for navigation, I'm constantly signed in to hangouts and reply to the messages through the watch, I keep a running list of to-do notes, etc. I also have the screen brightness set really high, because its usually off anyway, but it's perfectly visible when I need it (even outdoors). With a full charge in the morning and the brightness set very high, I have yet to kill the battery before I go to sleep, even when I've used the watch extensively all day long - which is good, because my use will only increase as apps are developed.
tl;dr Ultimately, they're very similar and you can't really go wrong. The extra 100mAh on the G watch is probably negated if you plan to keep the watch "always on" (in fact, I wouldn't be terribly surprised if the Gear Live even gets better battery life when the screen is always on). If you turn the display off, though, then the battery-saving display technology won't matter as much and you'll have an extra 100mAh of battery life.