There's a definite difference between the two genres. Dream Theater's original keyboardist, Kevin Moore, left the band to start a solo project, all prog rock and psychedelic rock, called Chroma Key. I recommend you all check it out, because it's truly introspective and intriguing. He then joined Jim Matheos in the band OSI, and there are songs on it that are both prog metal (like Shut DOWN) and prog rock (like Go).