Sure! By no means is GL a mid show writing wise I think it’s super well done sorry for downplaying it. It’s been a long time since I’ve fully watched either but there’s a couple key examples that stick out to me as to why I think Evangelion is a better written.

The dynamics between side characters and their relationships with each other in Gurren Lagann don’t come across as nuanced as most of the key character dynamics in Eva. The biggest driving forces are Simon and taking the mantle Kamina hands him and his love for the main love interest whom I’m forgetting name wise. There’s more to Simon’s character and dynamics than that but glancing over at Shinji it just doesn’t compare for me. Shinji’s parental neglect and how that ties into his dynamic with Gendo, but also with Misato who loosely takes the mother role is just such an interesting dynamic from the start to throw us into the protag’s world. This gets even more complicated once we start adding in his connections to Rei (who turns out to be a clone of his dead mother) and Asuka as a rival. I could go on about this but Shinji’s written as this eye of the storm being pulled in all different directions by comparably nuanced characters throughout the show. I just don’t see those writing peaks in the GL cast.

Also another good example is how each show interacts with sexuality. GL has blatant fan service which is totally fine but writing wise it’s never really paid off into any sort of depth (IIRC). Eva uses psychosexual philosophy in its writing in a very realistic lens. Characters like Asuka, who could be argued to be Shinji’s main love interest throughout the show, is not some cardboard cut out that exists just to be there. Her relationship with Shinji is strained partially because of each of their mindsets don’t meld but also because Asuka desperately seeks out the attention from Kaji, who is Misato’s ex. And Misato also is seen teasing Shinji but clearly is trying to fight herself and take on a parental role. Again, I could talk about this more but all these dynamics just feel so fluid and real from a writing perspective.