Certainly you should buy whichever one you like better. I have owned both and still own MM but plan on owning AFM again someday. I personally find AFM a little more repetitive and the shots a bit better on MM. i like the alternating ramp shots which both games have but I just can't seem to hit them on AFM reliably as they are very tight but they seem to flow very well on MM. I think shooting the flying saucer is a little more exciting than shooting the castle but on MM it just seems more fun shooting the other shots to light each madness and go for royal madness and AFM doesn't have the same sort of shot equality(my opinion). Martians are cool but I think trolls are a little cooler. I actually prefer the alien theme but both themes are amazing. You should try to play them both a bunch and then decide. Good luck.