Well I have done testing on the new Gold ones over the break.
Also there are two types of WD Red drives, Red Pro (7200rpm) and red NAS (5400rpm/intellipower)
You will not get a straight answer out of WD on what "intellipower" is other than it is a variable rpm rate that adjusts to demand but not to the speeds of a 7200rpm drive.
rulle of thumb its a 5400RPM drive unless stamped otherwise or 5400rpm=intellipower. But it does change spin speeds depending on demand how much we will never know Because WD wont come off of it.
the WD gold drives replace the "black and yellow" enterprise drives like these
they are one of the best most reliable drives out there along with being the most expensive.
WD red pro is my choice for Raid style storage for video of any size. this factors in cost and performance for the long term. just stay away from the 3TB ones for what ever reason only the 3TB drives have a high failure rate.
WD red NAS, Black, and purple are the drives I use for single or 2 drive "box kits" or 32 channel systems or smaller. its not worth it to spend any more on systems that small these days.
personally- I buy WD red Pro, Black and Purple drives for video storage, I like 7200rpm drives as they are the most stable reliable and cost effective drives for ME to use in my situation. Purple drives go into 8 or 16 channel systems I do on the cheap.
also on a side note do not use WD Green drives. they will fail after about a 1 and a half of hard use even on small systems. I had seen these drives pop up on "energy star certified" NVRs/DVRs. they are not worth the scrap metal they are made with.