Difference between overhead catenary vs third rail

[Milko]

Hi

The electrification via overhead catenary or third rail electrification, apart from the look and feel, is the same? The electric locomotives can use one
or the other without problems?
There are differences according to pak used?

Giuseppe

[The Hood]

In standard simutrans, the only difference is graphical - any electric train can use either.

In experimental simutrans, differences are enforced (but only if this is coded in the pakset).  Pak128.Britain-experimental has some electric trains which can only use overhead or can only use 3rd rail, and some which can use both.