Under no circumstances should you be wasting money on cables like Monster or cables which claim to be "high-speed", etc. There's no difference.
Now, where the cables are performing properly, there is no difference for that task. However, that doesn't mean that there isn't differences in the cables for other tasks or that cables with higher bandwidth and performance parameters may be necessary in some situations.
There certainly are cases where there aren't differences, and if they are performing properly for your task, that's one of them. You can't improve that.
However, where you need enormous bandwidth and need to maintain that over distance, cabling differences are much more crucial.
That isn't really in Monster Cable's favor, but I just wanted to clarify that it's a little misleading to say that there are "no circumstances" where higher bandwidth or higher performance cable isn't required.
It's like the difference between Cat5 and Cat5e/Cat6. It often doesn't matter at all, but indeed sometimes it does. Cat5e or Cat6 won't give you more performance if Cat5 is giving you all the performance you require, but sometimes it won't, and the improvements in cabling can become relevant in those situations.