For the same strings my rule of thumb would be to raise the tension 10% between an 18x20 pattern and a 16x19 pattern to get the same feel. It seems like your case doesn't fit with this rule.
Probably some of the difference is due to the strings and some is due to the racket. Could also be some quality control in the stringing.
In all, I'd be wary of both going back to the old strings and at the same time lowering string tension.