Some people say that initially having the patch 1.02 and later adding the new 1.03, theyt could see the improved gameplay in NV fallout but strangely another person complained about the game glitches still haunting the game as he downloaded the game when version 1.03 is out without any prior patches.

The question is: is it better to install the game from stratch (installing 1.03) and play or is it better to leave my old game file (consist of version 1.01 &1.02) and then adding the new patch 1.03 ?

All patches are iterative and include all previous ones. 1.03 does'nt fix anything btw, it only adds DLC trophies. The next one will fix stuff though.