Answer:
   
   Collective worship is critical in Judaism. There are actually two
   notions behind gathering to pray:
    1. One is praying as an individual, where the others provide an
       environment more condusive to that prayer. This factor was even
       more critical before the printing press, when many people also
       relied on the cantor to provide the words.
    2. The second is praying as a community. Not merely as a group of
       individuals within a community, but the community's prayer to God.
       After all, the covenant at Sinai (or, for non-Jews, the covenant
       God made with Noah as he left the ark) was with the community as a
       collective unit. There is a sanctity to the community that exceeds
       the sum of its parts.
       
   In both issues, the communal prayer is superlative over praying alone.
   Of course, other factors come into play. Someone broken-heartedly
   praying outside their child's hospital room, speaking to God from the
   core of their being is still the superior prayer over one who might
   feel confined from fully expressing themselves in public.