Which way to go?

I'm in a Rock Trio so I use a Micropog for the very thing you want.
Its all about blend with the Micro. It def can sound fake if you have too much of the upper octave but if you hit the sweet spot its perfect.

I use a Rat clone -- Micropog -- a little reverb -- the occasional Flange to get surprisingly fat & wide sounding when the G player takes a lead ride. (sometimes I leave it on thru the whole song )

PS: I've tried a lot of other options for this (not the Octron) but the Micropog has been the best by far ... still cant believe how good it tracks!

 

Check out the T-Rex Octavius. Similar to Micropog but less digital sounding. I have never played one, but it sounds awesome in the demos i've seen. I have played the two you mention. The Octron's upper octave is more of a distortion, and the Micropog sounds a little weird to me (and lags a tiny bit).

 

I have the POG2 and the upper octave is crazy funky. You might also consider looking at the Soundblox2 Multiwave Bass Distortion from Source Audio. If you are only going to use the octave with distortion, why not buy a distortion pedal that has an upper octave built in? There is a really nice demo by Will Cady on YouTube. I find the upper octave setting in the pedal a nice touch. Good luck with your search.