by szendroib
I have played through S03 and S04, and for me S03 scenarios were a little boring. The first problem is that the map tiles themselves are mostly just blue night scenes and some dark Venice city spaces. The maps all look pretty bland because of this. The bigger problem is that 5 out of the 6 maps are basically linear maps (one starts as a circle but becomes linear). Linear maps are not too fun to begin with, but they are eve worse with unknown momsters that can just clog up half of the map. Also S3 has Azatoth who is an awesome boss but boosts unknown monsters to silly levels :D. So I found S3 to be the worst season to use Unknown monsters with. It is a strange release. While I don't enjoy the S03 scenarios, the investigators and Azatoth are really fun. You also don't have a choice if you want to play with UM and relics. The sloth boss I'm not too fond of as he just wastes your actions, but the sculpt is pretty good.Now on the other hand S04 is probably my favorit season of the four. I found the scenarios to be quite fun and imaginative, also the locations are varied and fun. You have an airship, a real ship, a mansion with greenhouse, an egyptian setting, and one map has dimension gates between a desert and a winter region. The mechanics are interesting/fun as well. Also out of the 6 new investigators 4 are real favorits for me (I wouldn't ever play one of them though, but it is just personal playstyle preference). Oh yeah and I love to play against Nyarlathotep as well, he is a pretty fun GOO as he is harassing you on the board from the beginning of the game, and his "mini" is pretty stunning as well.
So I think it is a different situation than S1 and S2 where S1 is vastly superior, and S2 didn't even have any GOO. I think it is absolutely worth to purchase both new seasons. S03 for the heroes, 2 bosses, and the new mechanics, and S04 for everything.