The MyDigitalSSD BP4 delivers very good sequential read performance until the drive has a significant amount of data on it. At that point a noticeable decrease in performance starts a downward slide that negatively affects the user experience. That isn't the worst part, though. That honor goes to the inconsistent write performance that affects write latency and when you have high latency, you have low IOPS performance.
How did the BulletProof 4 go from such a good 2.5" drive to such a poor mSATA drive? It's all about the channels. The mSATA version is limited to just four channels and the 2.5" utilizes all eight channels. Personally, I think we are seeing the affects of poorly written firmware that isn't optimized for a four channel controller. I can't point to any one area and tell you with certainty that my theory is correct, though. If there are issues with the firmware and efficiency, then reducing the number of channels is an easy way to highlight them.
Going into this review we fully expected the mSATA variant of BP4 to deliver class leading battery life, but we know now that isn't the case. BP4 is really close to LSI SandForce's B02 at this time. Going forward into Haswell, BP4's battery life will look average. SSDs with DEVSLP will have a massive advantage since they'll drop to just .1mW and recover from that nearly nonexistent consumption state in 100ms. The new B02 controller and Plextor's new Marvell based mSATA drive both support DEVSLP. The feature isn't on BP4's product spec list, but it's possible for MDSSD to add the feature later. That still doesn't get around the write latency or the poor performance when the BP4 mSATA has data populating the drive.
The great equalizer though is the price and that's where the BP4 has an advantage over the competition. After researching, we found that every other current gen 256GB class mSATA drive tips the scales north of $200. A few are close to the $200 price point but most, like the SX300, M4, M500 and so on, are closer to $250. The 240GB BP4 mSATA we tested today costs less than $180 at mydigitaldiscount.com. With a $20 to $70 price advantage, the BP4 mSATA 240GB is very attractive for those looking for a bang for the buck mSATA SSD.