I use (1) ST_Length (ST_Transform (geom, 3395)) to get distances in meters from points in Geographic Reference Systems EPSG: 4326. The thing is I found that with (2) ST_Length (geom, true) you can get also the distance in meters but using the spheroid.
If I am right, is the option (2) more accurate if the GIS project use a Geographic Reference System for Global data, especially near to the poles?
ST_Length reference: http://postgis.org/docs/ST_Length.html
EPSG:3395 reference: http://spatialreference.org/ref/epsg/3395/