I pick between tectonic scanner and continental surveyor depending on the map.
Generally, one or two continents = tectonic while islands = surveyor.
Even with continental surveyor, you won't be sending the long sea trade routes until the ultrasonic fence quest, and you can only send the trade routes if the other capitals and stations are on the coast. I find that this is only worth doing in island maps, which mean more sea scouted and almost all capitals and stations are coastal.
Tectonic scanner is nice to locate strategic resources early, and early titanium mines. This can give you a nice jump start, and help you claim and not settle on strategic resources earlier.
For retrograde thruster, the extra land seen would generally be scouted early anyway, and the second ring city placement is usually no big deal.
Lifeform scanner may be nice for finding xenomass as harmony and being able to avoid aliens, however I generally don't have too much trouble scouting nests.
IMHO, the strength of these choices depends on specifics of the map, however you don't know the map until after you picked. Also, these choices usually don't have as huge consequences as colonist or cargo choice.