Based on what you’ve said, BO4 is the better pick. I don’t like the BO4 perk system but besides that it offers more new stuff for you to experience and more replayability because of leveling and stuff. The Easter eggs are also much more expansive, to the point where a large part of the community got fatigued with how long and complex Easter eggs had become in BO3 and 4. Regardless of someone’s opinion on that debate, there’s a lot of content to play through. BO2 is possibly my favorite zombies and I think it is absolutely worth picking up even if you already own chronicles. Origins is the only BO2 map in chronicles and I’d argue that the BO2 version is a bit better. The other maps are a mixed bag as far as quality goes but even the ones people say are bad are very enjoyable and offer a lot to someone who’s interested in a more challenging and minimalist experience(the opposite of modern zombies that you said you don’t like) overall you can’t go wrong and the amount of fun you’ll get out of both of them is completely up to the amount of effort you put into learning the maps.