Yes it is common to have difference between two pathology reports, which is why it's important to have slides sent to a well regarded establishment like Johns Hopkins as you have done.
With Gleason scores, the primary pattern is the first number (in your case 3) the secondary pattern is the second number (4)
The revised Gleason score does change your situation: while there was some 4 there as a secondary figure, the primary pattern of 3 is not regarded as high risk cancer.
The specialist would have considered your overall diagnosis and figures, including the % of cancer found in each core.
Choice of a top doctor is the most important consideration for the best prognosis possible.
I would do everything possible and if necessary travel or wait within reason to have the best surgeon available as he will provide best chance of fewer side issues, and have a huge difference to both short and long term outcome.