Oops. I'm not sure to understand what you said but here some explanation with my well-known "beach-English".
Because and and or have the lower precedence ( lower than = for example), it is for me simpler : no need to use extra parenthesis when they are used as 'if...then' way.
With && and || I always have to check 'perldoc perlop' to find precedence. So, OK, it's only my choice.
Some not tested examples I would write
And: $var=$den and $m/=$var
&&: $var=$one&&$two