This is disscuss about nothing.
Question about using pro*c (pro*ada, pro*fortran ...) or pl/sql doesn't exists.
We usually have only one basic question:
What kind of system architecture we are going to build:
- with havy client's component
- whth thin client
- mixed model (with balance between client and server(s))
- with deditated application servers.
...
- platform depended
- platform independed
...

when we decided for ourself this problem (or problems) we may make choises of
languges, tools ... what ever.

About faster/slover.
only 1 sql query can make a degradation of perfomance whole application in pl/sql.
only 1 loop in pro*c or struture of objects or memory allocation/deallocation procedure in c, can kill whole programm.