6TB External Hard Drive 3TB X 2 OR Dual Bay?

So I need to replace my two 2TB externals with 2 X 3tb External HDDs. My concern is that If I get one of these fancy dual bay or even quad bay (using the dual 2tbs I have now and then adding two more) external enclosures, isint there a risk of loosing all the data? Say there is a power failure, or the card in the enclosure fails or the drive falls over. Is it not better to just get two seprate 3tb hard drives? I am looking the mybook series USB 3 from WD. It has a kensington slot which is pretty much a muse for me should I buy that, or a dual bay enclosure or wait for cheap thunderbolt drives?

 

I use an AkiTio My Cloud Dual Bay NAS. It is RAID 1 capable so if one drive fails the other will have all the data, but this is best to use with blank drives because they AkiTio reformats/formats the HDD's you put in.

Akitio intros personal MyCloud Duo NAS server | Crave - CNET

Amazon.com: AkiTio MyCloud Duo Personal / Small Business 2Bay Network Attach Storage . Free iPhone/iPad Android APP Ready, RAID 0 1 JBOD: Electronics

 

Mine is a WD, it says 0209A, ack, that's all I can really find on it. I think it's only a terrabyte or something like that, too? Ack, my mom got it for me years ago, but her deciding factor was how well it handled backing up everything automatically - even though I don't use that feature. X) WD seems awesomely reliable though, this is one of my favorites. :0 It saves me so much frustration.