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Fair enough, gkellum.  Since I threw the gauntlet down…

Yes, I've tried the Lou-nivibe (12:2) in the ModFactor as well as the Fulltone and MXR models against a vintage (borrowed) Shin-ei Uni-Vibe and my own home-built unit based upon the original circuitry.  All "challengers" sound flatter with not as much lumpiness or lop-sidedness even with the intensity turned to maximum.  They're not bad, they just don't go far enough into the hippy, trippy territory.

The original Shin-ei Uni-Vibe was a four-stage phaser which employed light-sensitive resistors (LSRs) driven by a lamp and LFO to control the phase sweeps.  The first three cascaded stages had the same notch frequency while the fourth had a slightly higher notch and didn't sweep as far (it also buffered the phased signal before hitting the mixer).  Since the LSRs were not matched (as far as I know), the sweeping was slightly different which created pleasant beat frequencies that a two-stage simply cannot recreate.  All the other remakes (with the exception of the out-of-production Dunlop Uni-Vibe which copied the original circuit including the LSRs) use FETs which, while having a similar transfer function as the LSRs, are too close in their variances/tolerances to create the sometimes-very intense beats of the original.

Perhaps if the phaser algorithm was expanded to include four stages with "intentional" (and possibly controllable) variances in their notches and sweeps, the same level of warble and beating could be achieved.