There's lots that delenda does differently but there's something I think is really great. It turns "upgrades" into choices. For example not all the technology upgrades in the forge can be used, you must choose a path. I only started playing in the beginning of June but vanilla 0 a.d. feels a lot less dynamic, which is fine. I just wanted to mention something that delenda does differently which I appreciate most and allows me to have more unique experiences per faction than I can in vanilla.
Thanks and personally would love more decision making along this line which you are locked into but I am happy regardless, especially with how easy it is to toggle the mods anyways.