There are two things about song...one lyric and two melody (music)...While both are important ingredients of a song, each has its role...while lyric gives meaning and mood and music sends that message deep....
Now the comparision of mastreos....LaxmikanthPyarelal duo and Pancham....i feel we are not qualified enough to compare until we understand the genre they represent.
We, Indians relate themselves more with Hindustani.....LP's strong point....but there is a problem with this that the composer will become naturally inclined to certain raaga all the time in his composition....its kind of mother and child relation.....once you start composing...we start falling in love with it....
Sachin da and Pancham da are two composers who experimented folklore and relied more on melody while keeping compositions less dependent on Hindustani...this is the reason why when we see the quality of music with Lyric in mind, LP's composition may seem superior...but as far as reachability is concerned..it requires mesmarizing melody which SD and RD are UNCROWNED KINGS at.
Take me,...i am a telugu and place i belong no body speak and understand Hindi....still RD's music is very popular here...many people are like me who keep those pancham's compositions close to heart...... only when i married a north indian did i learnt hindi and could understand why musicians like LP , Roshan and ShankarJaikishan are so popular in Hindi music....
but still Pancham will remain with me.....bcos thats the music i have grown up loving....