I normally try to stay out of these threads because I wouldn't want my presence to keep people from expressing their opinions freely. But I thought I might be able to give some details that might help you decide what fits your needs.
The Xerograph Deluxe is a much more feature-rich filter than the filter in the Subterranea. The Sub's filter only operates on the traditional octave voice, not on the synth voices. The Sub's filter is only controlled by a cutoff frequency knob and has fixed resonance, whereas the Xero Deluxe allows you to control cutoff with a knob, an expression pedal, and/or your playing envelope, and it has variable resonance. The two filters are also totally different in design, so they sound different. Think of the filter on the Subterranea as an extra-deep tone knob for getting more versatility out of the "OC2-type" sound.
I couldn't compare the sound of the Octron because I haven't used one, and it would be improper for me to offer my opinion on somebody else's product, but the Octron does have an octave up voice, which the Subterranea does not. The Sub instead has the unison and octave synth voices with variable waveshaping.
The idea behind the Subterranea was to be used in concert with a separate filter, much in the way that a traditional synth voice is made by sending a harmonically-rich oscillator with sub-osc into a resonant filter.
I hope that helps differentiate the feature sets of these pedals.
By the way, you'll be able to purchase IE pedals in about a month.
I just wanted to get wait times down because I know how annoying it is to wait forever for your new pedal, so that's what we're focused on right now. When we reopen things should be in stock, ready to ship.