Generally speaking with our model engines there's not enough difference for one to be called a long stroke and another short stroke. The thing that makes the difference though is not the length of the stroke but the fact that the bore is bigger in a "short stroke" engine. The circumference of the bore increases by a factor of pi (circumference = Diam x pi) so this means that even though the height of the ports is slightly less (for the same timing) it's more than made up for by the extra room around the bore for these ports. This means they can have a bigger area for gas to flow through them which gives better breathing at higher revs. It hurts low down torque though because the velocity of transfer mixture is lower.

A 2 stroke model engine designed for low down torque won't necessarily be a "long stroke" but it will be timed differently and the ports will be smaller (including the transfer passages) to keep the mixture velocity high. A good example of this is the latest OS LA's which have done away with the boost port so now the mixture has to move faster through the remaining two ports.