Vandersteen 3a sig vs. Paradigm studio 100

Do you think this would be a step forwards or backwards?
Step forwards but a small step.
Vandersteen is a much smoother performer, the Paradigm has it fans and is a great speaker but is no doubt an easier speaker to have problems with fatigue. With the 3A and the Vandy sub combo you have pretty much a Quatro wich is a speaker you could easily live with for the long haul.
I have Vandy 2Ces and used to own Paradigm 100s 1st version. The Vandersteen is a better speaker in many ways including the fact that it is time and phase correct. Plus it will extend lower with good amplification.
There's little question the Vandersteen sounds different than the Paradigm, but that is no indication that one is technically "better" than the other.

Depending on your musical tastes, I'd take the Paradigm and pocket the savings.
Do we think it is a step forward or back? Well that depends on which one you currently own. And you don't even give a clue as to which that is.....

I have the vandy 3 sig.
If you like the Vandy sound it might be a risk to go to the hotter sound of Paradigm, as I said earlier you could find it a fatiguing speaker in comparison.
Chadnliz has it right on; I own the 100s and have come to like them but only after moving to a tube amp. With a SS amp their tweeter made me nuts. Very different sound than the warmer Vandersteens.