The Pro-197 & Pro-652 are virtually the same scanner. Both will cover the same frequencies and system types, and use the same programming scheme. The Pro-106 and Pro-651 are also virtual twins. Operation, programming, and capabilities the same.
The PRO-106 is essentially the same radio as the PRO-651 (as well as the GRE PSR-500 and the Whistler WS1040). The PRO-106 was made by GRE (as was the GRE PSR-500). The PRO-651 is made by Whistler (as is the Whistler WS1040).