They are so different, yet Moog's in their own right.
In the Voyager you get an instrument with a better feel (wood helps), much nicer keyboard to play, full knob job, Midi, loads of patches, 3 osc's (I love 3 Oscs patches), build and engineered at the right time, well almost. It was late enough for the product to end up a "modern" product, yet it has aged somewhat in terms of in-house technology. Seems awfully complicated to add arpeggiator for reasons that are probably not foreign.
On the other hand, the LP benefits from 5 more years advance in circuitry, plus Bob's direct supervision. IMO, it kicks the socks of the Voyager in bang for the "Phats". Absolutely a breeze to use even with it's fewer knobs. I find the Phatty more bassy. It's well made, sturdy feeling (keyboard a bit cheesy). An incredible success for an entry level lower cost machine that delivers big Moog sound. If it had a third Osc, it would overlap dangerously in Voyager territory. And now the LP has 5 CVs out.... OMG!!! Not a diminutive instrument, no sirreeee bob!
I want the Voyager in my living room for nice playing and practicing, and long time messing around with knobs... then bang the performance out of the LP...there should be one of those things around every next corner.
So no one really knows what the next Voyager will be, or the LPS3. But the LP is moving around, and going places. A better choice as a platform IMO for a major successor in the Moog line up, whatever name it ends up with ( or number of voices

).