I just noticed this when redesigning my high speed colony ship to take advantage of my latest round of space savings.
I am a capacity freak, with every chance to lower mass or increase capacity, I take it. So with only the last portions of the tech trees left to research in my game I have these values.
Deep Space Support
Mass:4
Cost 52
Maintenance 0.2
Range 39
Value 1
Support Field Generator
Mass 4.8
Cost 111
Maintenance 0.4
Range 46.8
Value 1.3
So, in dividing range by mass (my estimate of efficiency) in both cases, you get 9.75, so for both technologies, per unit mass used, you gain 9.75 range. However, Support Field Generator gives you the same range, at over twice the unit cost, and twice the maintenance cost. Bumping the range for Support Field Generator to 48, and an even 10 range per unit mass, would give some justification for using it. As of right now, my enhanced colony ships will keep their Deep Space Support units.