I had so much fun comparing these two octave pedals! After I give my review, I will reveal which pedal I ended up going with (sadly I couldn't keep both and the Sub 'n' up was borrowed from my classmate and bass player Fabian, thanks Fab!).
Build: the Micro POG is definitely bigger and also slightly sturdier (better for gigs and no worries getting scuffed on the edges). I really liked the size of the Sub 'n' Up and it was not really cheaply built or anything but because it has the paint around the whole pedal, it looks prettier, but then there is more paint to scratch off. Micro POG wins.
Foot switch: the Micro POG (and also other Electro Harmonix pedals) have a very stiff foot switch. It has a big click and needs quite some force to click it. Sub 'n' Up just feels more friendly and sensitive. Sub 'n' up wins.
Tracking: both are fine, with a slight delay, but expected I suppose. So it's a tie.
Sound: Sub 'n' Up in general is a smooth-sounding octave pedal has issues with gain. Micro POG octave up sounds a bit bright, but it tracks very well and you have a lot of gain to play with. The octave up also sounds a bit organ-like on both, so I think there is no winner for the upper octave. Sub 'n' Up has a more rounded sound but doesn't really help the sound to stand out. Overall sound-wise: Micro POG wins.
Modes: Sub 'n' Up has a few modes, but I kept it in polyphonic, since the monophonic option tracks really slowly and doesn't suit the electric cello. The TonePrint function I didn't even try, so I can't say if it is really good or not. Sub 'n' up also has an option for a sub 2 octaves down, which is a very cool option, but wouldn't say it was a deal breaker if my octave pedal didn't have one. The cello plays very low already (and I have an extra lower bass string) so I don't really need it. I prefer having one octave up and one octave down for the cello. Sub 'n' up wins for extra functionality.
The charger: I wouldn't usually need to mention such a trivial thing but one big 'con' about the Micro POG is that it uses a very big and heavy adapter with a very thin cord which is 220V and not recommended to be used with a 9V daisy chain. It's really something I hate about the Micro POG.
Overall: in the end I chose the Micro POG because of the sound. It felt more raw, and analogue, and consistently loud on both sub and octave up. Sub 'n' up sounded more digital, smooth, safe, and the sub was loud but not defined, and the octave up was not loud at all even at the highest gain.
The cello in the photo is the NS Design CR5 5 string electric cello by Ned Steinberger.