(I am a student pilot, so take this "advice" only for what it's worth.)
I think most would agree that you need experience in both environments. I am learning out of a controlled airport(RHV), but did touch&goes prior to soloing at a neighboring uncontrolled one (Q99) so we wouldn't have to deal with all the traffic and delays (for those times we went full stop). This got me plenty of experience in both environments, as I obviously had to fly in and out of my home airport.
It seems natural to me, though, that someone who flies out of an uncontrolled field would mostly stay there, and only venture into controlled airspace for the sole purpse of getting that experience, thus not getting as much exposure.
Thus, the answer would be "controlled."