<font face="Verdana, Arial, Helvetica, sans-serif" size="2">Originally posted by notsosmart:
Is it immigration that is the biggest holdup? </font>
Yes, that's the difference between T3->T1 and T1->T3. You could be in line for as much as 45 minutes to clear passport control at T3 before moving to T1. Going the other way, it's much faster.