I just purchased and setup a new 4M2 drive and it works great with my softraid software but I noticed the ThunderBlade on the OWC website. After looking at the specs it appears to have the same performance as the 4M2. Why a different drive with the same specs?
The only difference I can see is that the TB doesn't appear to have a fan so I assume it doesn't generate heat. I've noticed that my 4M2 gets pretty warm at times and I don't think its the blades that get hot.
Is there something else about the TB I'm missing?
The Thunderblade is a sealed unit, so it can achieve its performance with zero noise. This is important for many studio/audio editors.
4M2 is more for casual enthusiasts, who want to build their own and noise is not an issue.
Blades generate a lot of heat.

