I once had a Record Doctor II and a Nitty Gritty 1.0, and I can tell you that the Record Doctor is definitely not as nice.
With the Record Doctor II and the Audio Advisor formula that comes with it, you have to clean each side of the record three (3) times. (Wet, use the brush, flip, vacuum completely dry, and repeat.) You will hear a difference on old, uncleaned LPs after that point. It was pretty obvious to me. If you don't, the problem will be elsewhere in the system.
Also, record cleaners will not reduce the record noise that comes from damaged records. If anything, they accentuate scratches. BUT, you get a lot more information out of the grooves across the board. This may be relevant to what you have been noticing.