SSHDs are just fine for their intended usage. In your case, since you have the option of a pure SSD, that is the option which will give you the best performance. An SSHD has a limited buffer for items that will be sped up. This is important if you have the space for only a single drive, but want the advantages of both space for storage and speed for your OS, such as on a laptop.
You will likely see the same or very similar performance from a 7200 SSHD as you would a standard 2 TB hard drive for gaming, making the extra cost rather pointless. An SSD however, will improve the read performance across every program stored on it.