Hey there, Matt225.
In my opinion this is a matter of personal preference and budget. You can get 2 SSDs if you want, but I guess that for gaming - a 2xSSD RAID0 is a bit of an overkill. Get a smaller SSD for the OS and one with a larger capacity for your games.
Having in mind that the noticeable difference in performance while gaming, when it comes to the drive is generally the loading speed of your game and in-game loading screens - the other option is also a viable one. So if you'd like to go for some extra storage capacity, but compromise a bit with the loading speed (which in my opinion is also OK), then you can go for the SSD + HDD combo.
Overall, as I wrote above, this is a matter of personal preference mostly and there's no...