No wonder very smooth lah. Sometimes how the engine is put
together matters alot too. 
However LS430 V8 DOHC 280 bhp, 417 NM Torque sis till much smoother
with much more power to boot.
V6 SOHC 245 bhp, 350 NM Torque =S350. Your father's car is at most
a S350
V8 SOHC 279 bhp, 400 NM Torque = S430.
So if we compare the LS430 & S430 (same capacity), it can be
seen that the Lexus engine has 1 bhp more and 17NM of additional
Torque.
