nah. they differ in character apparently but sound obviously moog. Sub37 has 2 osc's that can be uncoupled plus a sub. 2 little phatties would give you 4 oscs, two voices with two osc's.
Polychaining the 2 would result in a 2-voice "true" polyphonic synth. You'd need to feed the raw osc audio out of one Phatty into the other Phatty to get the same paraphony effect of the Sub 37.