Difference between two 850 Evos

So I just got the Samsung 850 Evo SSD. I noticed at the last minute that there was a difference between the model numbers - there was a $113 drive(prices are high here) with a model number of MZ-75E250B/AM, and a $125 model MZ-75E250BW, which I got(I got it for $112 in a last-minute deal).

Why was the 75E250BW more expensive? Does it come with any extra goodies? Which one was the better choice?

The SSD itself has a model number of just MZ-75E250.