JBL has a wide range of guns, some very underpowered, capable of taking only small soft skinned fish at close range. There are other guns from JBL with more range and more power. I have the 38 special woody and used their mini magnum, they have their limitations but are a good value. Both worked well for the average fish in my waters. For the bigger fish, I needed the flexibility and power of the Riffe, and I paid for the better gun. Did I need it to put more fish on the table? no, does the Riffe get more fish that are not ideal shots? Definitely.
If the price difference will keep you out of the water, go with the JBL. It will work fine for the good shots you'll find in those extra dives. If you dive enough anyway, the riffe will get those fish that are a little faster, further away, bigger.