izigame.me

I personally find this dlc fun but do see a lot of the reason why people dislike it so heres my perspective on it. I feel this dlc is best if you are first off using mods and secondly doing a challenge run like i do where all disasters are set to max. The underground when you expand into it will effectively act as a backup life support system for providing water and oxygen during disasters because the underground isnt affected by them so you can hold massive reserves of water and keep moxie's down there. I also find it pairs very well with tech mex despite the mod adding no new techs for below and beyond because tech mex extends the late game research greatly which gives you vastly more time to expand and exploit the underground whereas in the base game you probably already have every single wonder as youre finally exploiting the special items in the underground.
If you are someone who heavily mods the game and likes to have max disasters then I recommend below and beyond because it gives you more options when it comes to building out your colony and ensuring its survival but if you play vanilla without any modifiers Id probably skip out on this one as there isnt really much reason to go underground in a vanilla game.