Both are great shows made by GAINAX, but I highly watching suggest their prototypes as well: Gunbuster and Diebuster. All four are great Mecha shows made by the same studio and it's fun spotting the similarities across all of them.

What I consider to be a spiritual successor to these GAINAX mecha shows was the most recent Gundam series "Gquuuuuux" which shared many staff members from them and has plenty of homages that were fun to spot! Also had the same mechanical designer as the Evangelions so I got a kick out of that.