Different size motor (540, 380, 370 etc) also different.
T-rating seems like an old fashion brushed motor definition that is now used in new 540 brushless definition. But maybe a better way to look at motor is to look at,
a) KV
b) power rating (Watts can handle) (volts x current)
c) max current (continous current and instantaneous "burst" current)
d) weight of motor
Typically, these are basic items for use when working with other RC models such as planes and boats.