Yes, it uses the same engine and gearbox. The technical difference would be on the headlamps (projector) , Steering (Electric Powered Steering), claimed to be more fuel saving due to using EPS and more "aerodynamic". Basically, If your 1st Gen Myvi is working fine and not much problem, I wouldn't recommend you to change to the 1.3 LB Myvi since the difference is not much. Maybe changing to a 1.5 one would make more sense but again, the difference would be only be on the engine and power as its a 1.5 Engine.

this is wat in my mind too. found some great discount during this year end promotion.
EZi discount around 2500 to 2700
EZ discount around 2000

any other member got higher than this?

If on paper or general knowledge, 1.5 would generally consume more fuel compared to the 1.3. HOWEVER, it really depends on your right foot. Some of our 1.5 owners are able to get better FC compared to the 1.3. If you are really a petrol head and wish to really save fuel, U might consider the Mitsubishi Mirage which Mitsu claimed that it is a very Fuel Efficient ride and is known as a Eco Car.