The EARX is the old model with 3 platters, the new model is the WD20EZRX with 2 platters. Fewer platters means less noise, heat, vibration and a lower chance of failure. Vibration is a big part of why HDDs fail so the vibration from one hard drive next to another can cause the other to die.
If the hard drive's role is as a non system drive with occasional light access then a Green drive should be fine.
But I wouldn't get a Green drive to run with Linux as the file system access profile can cause endless head park / unpark cycles.
The WD Reds are the same as the Greens except the have anti-vibration technology and don't park their heads by default. You should disable their default 7s error correction timeout before using it in a non RAID computer setup.
The other Barracuda drive you mentioned is a triple platter desktop drive. It will be louder, hotter and faster and may or may not be what you're after.
The 2 platter ST2000VM003 looks like a good option if you can find it for a reasonable price.