[marfish]

Combat Sense
RANGE TYPE DURATION DV
Touch M S 3
...added to the subject’s Defense Rating and dice pool for Surprise tests (see p. 108) as long as the spell is sustained.

Armor
RANGE TYPE DURATION DV
Touch P S 4
...add net hits to the target’s Defense Rating.

Vehicle Armor
RANGE TYPE DURATION DV
Touch P S 6
...increase the vehicle’s effective Armor by 1 per net hit.

Comparing Combat Sense and Armor, there is no point to take the later.
Comparing Armor and Vehicle Armor, there isn't anything to stop me from just using Armor on vehicle or drone, so what's the point of Vehicle Armor?

The spells needs some erratas.

[Stainless Steel Devil Rat]

The difference in drain between combat sense and armor is due to the type. Mana spells have less drain than physical spells.  Yes, the mana spell has the expanded effect, but in the grand scheme of things bonuses on a surprise test aren't hugely valuable because being surprised in 6e isn't that big a deal.

You are right, however, about vehicle armor.  And that's why it already has been errata'd! Vehicle armor gives hardened armor now.

[Typhus]

With the optional rules in 6WC, I would also suggest that the Armor spell would work to improve any armor-as-damage-mitigation rules you might be using, since it's specifically working like armor.  Whereas Combat Sense would be affecting the Reaction side of the DR calculation, and thus would *not* affect the armor.