Chillys mod is from an earlier version of the game so in terms of polish I would say that the original version is better in as far as navigation and shows a clear progression in the scenes. If i remember right nergals version was almost dead for a long time and when it finally was finished they were basically 2 different games that started out mostly the same.I played it and after a while I back to original version. Because that version didn't feel well. I mean it has a lot of content but womans make me feel like they are already corrupted. There was no boyfriend for Kaylee and it was too easy to take handjob from Sarah. But I still think extra characters was good.
Edit: What do you think about Xalenda Mod? I read it's page but I'm still not sure what it really change instead of Master/Slave system.
As far as xalendas I would say his mod is a mod of a mod from chilly. It's got interesting story that is different from the other two but it has a lot of bugs that need to still be worked through last I played. Some have patches and other people were helping by uploading fixes but it isn't done.