I released an album online and on CD back in 2014 that I produced entirely with Nanoloop on iOS, and can definitely share an opinion. The iOS version, including how you use all the functionality of the step sequencer is really different. I used it to make a more electro type album rather than a chiptune album. If making a more proper chiptune sound is your goal you're probably not exactly going to get from this what you would on the Gameboy cartridge version. I actually can't stand the Gameboy version compared to LSDJ as far as that goes, but the ease of control you get on the iOS Nanoloop is pretty awesome, and the real kicker is that you can import libraries of samples with relative ease. Furthermore, Nanoloop on iOS will let you tweak and alter those samples in lots of ways including pitch bending them on the fly.
So, my music kind of sucks I guess but the project I did was a bass CD (if you ever were familiar with the Bass Mekanik era where chest rattling car audio was a thing.) Just check it out:
http://bitpusher2600.net/g33k.html
The entire thing was produced purely in Nanoloop. You get simulate a chipish sound alongside more common electronic instrumentation (such as my tune Bassik Protocol) or pitch bend a couple samples and tweak timing (such as my tune Moonlit Bass which gives a small spectrum of piano notes.)
So there's that. Long story short; Nanoloop on iOS is fantastic and worth way more than its cost (in my opinion) for making all sorts of different styles of electronic music once you learn the many ins and outs of the software and realize just how much you can really do (the learning curve of getting the most out of it isn't what I'd call small.) If however you're wanting to make straight Gameboy music, this works practically nothing like the Gameboy relase whatsoever. Yeah there's a grid of squares that represents a step sequencer, but how the two work and getting around the software, nothing alike.