I might be wrong about this but part of my point was (that I failed to mention) I don't think the FPS is the same in windowed vs full screen modes. If somebody wants to correct me on that by all means please do but I'm pretty sure it differs in one mode vs the other. I would expect it to be higher in full screen but maybe I am wrong about that. My reasoning there is the operating system has to keep updating the desktop along with the game when it is running windowed whereas full screen I presume it does not have to draw anything to the screen but the game itself.
Anyway, if that is useful to you then good enough. I think I read somewhere, maybe it was you who posted about it, that the game is a very demanding one. I wrote elsewhere that it seems to me that one has to figure on upgrades of Mac hardware roughly every three years to be able to run demanding current games just as a general rule of thumb considering that with mobile GPUs we are starting in the midrange for performance the day we buy them as brand new for the current model year. So by three years they are bound to struggle with anything pushing the envelope.
You might want to try running the game full screen and measuring with Steam to see if it does any better or not that way although maybe it is just too much anyway.
This kind of expensive upgrade cycle has me seriously considering a Mac mini next time around with a screen that can be used for it, consoles and possibly a home built windows gaming PC. The funny thing is (sort of) you can purchase everything I just listed brand new for less than a tricked out current model year 27" iMac would cost. That said, this would be a complete no-brainer for me but I do like having just one machine to deal with. I have over a year to think about this so I'll just see what the next Mac Mini refresh looks like, etc. Even on one of those, I could actually play a ton of games I currently own, particularly most of my GOG games but even a fair amount of less demanding Mac stuff by the time the Mini is refreshed I'd suspect which would be cool. I might just do the Mini and a console initially before spending on a PC build I may not really need. This is just stuff I'm mulling over for the time being.
I love my iMac but gaming on a Mac is an expensive proposition with less than optimal results to boot unfortunately. I'll never use a PC again for everyday stuff but I might for gaming if I am not satisfied with a mini/console setup here.
