Upgrading to 6 TB disks, but which?

Posted this in another thread, but this is a better place.

The slowest drives in my array are 3 TB WD Reds, which are probably held back a little by their 5900 rpm? and a 5400 rpm 4 TB Hitachi.

I plan to upgrade some 3 TB Reds to 5 or 6 TB ones. What do you recommend, 5 or 6 TB? Are Toshiba X300 any good? What platter size do they have? And what about warranty and replacement? Should I deal with dealer or directly with Toshiba? I am in Netherlands and only WD offers advanced replacement but it takes close to 2 weeks before I get a refurb one. I already have a 6 TB parity.

FWIW, I have a mix of 3TB and 6TB WD Reds in my array.  The 6TB disks are significantly faster than the 3TB disks due to their higher areal density.  I'm pleased with them overall, though I did have to set them to not spin down in my setup.  I'm going to have to retest that with 6.1.4.

As noted, the 6TB Reds are notably faster than their lower-capacity cousins, due to the 20% higher areal density (1.2TB platters vs. 1TB platters for the 1-4TB versions).    For extra $$ you can also eliminate the slower spin rate => the Red Pro's have the same areal density but spin at 7200rpm.

FWIW, I have a mix of 3TB and 6TB WD Reds in my array.  The 6TB disks are significantly faster than the 3TB disks due to their higher areal density.  I'm pleased with them overall, though I did have to set them to not spin down in my setup.  I'm going to have to retest that with 6.1.4.

My mission is to replace those 3TB first and NOT with WDs at all. Had too many drives failing, getting a refurb as replacement which failed a 2nd time. Yes, they offer advance replacement here in Holland, but going through Germany it takes then 2 weeks to get me a replacement. This happened to both 3 TB and 4 TB drives.