userTransaction or JDBC transaction

Hi,

     please give suggestions...      


We are using a application server with connection pooling
jsp and servlets are used in project
for transactions Is userTransaction is better or JDBC transaction is 
better


userTransaction may be implemented like this 
try
{
getUserTransaction
transaction.begin
execute queries
transaction.commit
}
catch()
{
  transaction.setRollbackOnly
}

JDBC Transaction may be implemented like this 
connection.autoCommit=false
try
{

execute queries
connection.commit
}
catch()
{
  connection.rollback
}

which is better for scalability and performance when we have to use 
transactins 
in jsp/servlets

regards