I think a really fun experiment tends to be using carryover.
For instance - take your best set of 5 in the smith squat. Drop it and work on the freeweight squat over 6-8 weeks improving capacity. Now - if the free weight squat was effective, you should be able to get in the smith and within some weeks of reacclimation set a new personal record. I'd say, this would be very common, repeatable, and would be a valid expectation.
Now do the reverse, take your best free squat set, work exclusively in the smith getting a solid increase over time, and transition back. What generally happens is that even after some reacclimation there is no new PR, sometimes performance just drops to the crapper in the regular squat.
Obviously, this isn't as valid for a novice where anything can work and give progression (free squat will still outperform smith though), but that's kind of a good way to look at these things. If something really worked to make you fundementally bigger and stronger, you'd see those increases in the core lifts in fairly short order.