Hi - I was waiting to see if anyone is choosing between these two as technically we're not. DD was on WL at G&L and we were clear on LU. We had a problematic experience at G&L on the test day and were quite soured - i.e. I am biased! That said, every parent of a DD at G&L on here has said great things about their and their DD's experience at the school. Maybe they've PM'ed you about the choice you're making, but since I hadn't seen I thought I'd add.
I think the schools are so different it's hard to compare. From my outside perspective, G&L seems to be more of an intentional community with houses and weekly messages (I think they call them 'epistles') from the Head while LU seems to be more of a mini-town with the DC exploring and finding their own communities. I don't think there's a weekly message from the Head though I think there is consistent communication about activities relevant to each DC. I've heard both have had pastoral issues in the past but both have done really well in addressing them.
So beyond co-ed, I think size and feel are really different. My impression from a couple visits to each school is that LU is more diverse from economic, ethnic, international, perspectives etc.. But I have limited knowledge of either place and have not done a systematic demographic study.
I do really like the emphasis LU has on its bursary program - tho I do wonder if the bursaries come with the expectation that the recipients have to 'pay it back' since they seem to have a lot of gratitude videos and posts with the intention of raising more money but I cringe at the idea that the kids may have to perform for their supper. I have no idea how it works but love the fact that they want to broaden access. I think they do quite a lot in the community too but that's from their Instagram feed.
G&L seems to have a lot of talks and highlights on successful women in various disciplines and careers. It may be easier for the girls to get involved in things there as there may not be what might be overwhelming number of choices for the younger years. Again, I'm not sure. I remember LU tour guides saying that they signed up for far too many clubs and had to cut back, but I didn't hear that anywhere else. I also asked them if they went to any of the multiple talks that I saw signs for and they didn't go. That may be the case at other schools but I did feel that may be an issue of size and options at LU. I get the feeling the Head isn't all that engaged in the day-to-day while from what I understand the G&L head is quite hands on. I assume it's how the schools are run rather than expecting this to shift with the new head at LU, but we'll see.
Academically I think they're quite similar. G&L tends to perform better on the tests but LU tends to have better university entrance...maybe?? I can't remember where I got that impression though so take it with a pinch of salt!
As others have said, go with your gut. Where do you and your DD feel would be best for her? I'm sure she'll do very well at either place so it's really down to what you think is best fit. I think we're strongly influence by having spent a couple decades in the US and seeing friends' kids go to huge schools and come out having had so many opportunities and found their niches.
I'd love for other people to weigh in if you're still asking!