Given that this is the Gamo gate, I didn't immediately think of this line of reckoning, but I had both a Whisper (tuned) in .177 and have a BAM B-26 in .22 (from Melick) and I still have the B-26...
Jeff knows much more about airguns than I, so there you have it. With the BAM, you get a far better stock trigger, and a smoother shooting gun. It's solid, and pretty powerful in the .22. The Whisper can be tuned for higher power perhaps, but I did not find much to prefer between these two.
You'll know you have a plastic gun if you buy the Whisper, and the trigger and the bundled scope with the "deluxe" are both seriously inferior elements. Apologies to Gamo fans...