Yup, just that the design is different.
If you look at it comparitively, ERL (KL) has 4 cars for all
trains while SARL has 3- and 4-car EMUs. For KLIA Ekspres, 1 car
for baggage and 3 cars for seats. For KLIA Transit, 4 cars for
seats. For SARL, City Line has 3 cars for seats and Express has 3
cars for seats and 1 car for baggage.
Thing about the Desiros... They feel uncomfortable. Have taken
them in Europe, and heck, never again. It was just like the metro.
No different imho.
Are the KLIA and SARL ones smooth? The rides I took were hell
jerky.