The statistics that I see (
https://www.tfmstats.com/corporations) suggest Interplanetary Cinematics and Saturn Systems are equally "overpowered". Only Point Luna has a higher win rate for players with 500+ Elo. Remove that selection for expert players, and Interplanetary Cinematics turns out to have the highest win rate overall. The real difference that I see: base game has more underpowered corps. The worst performing Prelude corp, Robinson Industries, is still pretty decent.
I haven't seen the discussions between the gurus. But I believe the game is a little poorer with this Prelude corp exclusion. Also, the risk of getting a choice between two poor corps is higher. It's still not huge - it's happened only once to me this season that I got a choice between UNMI and Phobolog. It does partly explain the recent post*
I wish this game had a mulligan system, though. Over time, the luck factor should even out, both for this kind of risk of drawing two poor corporations, and for getting strong corporations in the opening choice if Prelude corps are included. In all, I'd be happier with full Preludes, or base game only, instead of this compromise.
*
https://boardgamearena.com/forum/viewtopic.php?t=50135