The only difference between the 84+ and the 83+ (besides the more modern looking case), is the amount of archive memory and the faster processor. The 84+ has a processor that is 2.5 times as fast as the 83+. It has three times the archive memory than the 83+. It also has a USB port.
Benefits of the Silver Edition (SE)
The Silver Edition of the 84+ has nine times the archive memory of the 83+. Otherwise, it is identical to the normal 84+.