I’ll try to approach both individually and leave out the OT as that’s a completely different beast and I mainly use it end of chain anyway as a mixer/master effects thing.
For me the comparison is between the DT + DN and AR + A4. I’ll say at first that I think they’re all awesome machines, and there’s enough difference between them, especially the DN and A4, to warrant having all 4 if you were so inclined. But there’s also a lot more similarities for me that made no sense to have them all. Plus I’m not made of money.
For the AR, one of the biggest selling points was the fact that I could make my own drums from scratch, but also layer samples on top. I love dialling in a sound, tweaking it, blending in a sample and tweaking that and just basically coming up with whatever I can or can’t imagine. I get a lot more enjoyment out of making sounds than flicking through samples and messing with them (though you can do a lot of what the DT can do in that regard on the A4, and whatever it can’t the OT can more than cover). The compressor is also amazing as is the distortion. It’s probably my favourite machine that I’ve ever owned. Also the VCO they introduced on it makes a really mean bass. The DT covers the sampling part better obviously, but there’s 0 drum synthesis and all the other bells and whistles that I wanted.
With the A4 it wasn’t as cut and dry as it’s a completely different sound. The DN is in many ways, depending on what kind of music you make, more flexible due to having four more voices. But in most other ways, the A4’s modulation and sound shaping options far exceed it imo. Per voice you get 2 LFOs and envelopes with 2 destinations each (on top of an LFO for vibrato and 2 for pulse width modulation), 2 oscillators and subs (easy way to hack in some chords if you want to get around the 4 voice limitation), 2 filters, awesome overdrive, and a whole load of other stuff that let you shape all kinds of crazy things. I think the DN is better for pads and airy type stuff and the A4 is a lot more aggressive, which suits me perfectly, but is also capable of some nice pads and also getting into really experimental territories.
The biggest factor for me though was the performance capabilities of the analog machines. Being able to have a set of fully customised performance macros has been the most fun part of all of it for me as one of my biggest qualms with the digi boxes was the control all thing (partly due to my own constantly forgetting to save before I did anything). I mainly use the machines to jam and the performance knobs and pads are what really make it shine. The sound design on them has also led to me using them in a lot of songs that I’ve done as I find it easier to come up with what I want, on the AR mainly, than on whatever drum synth VST.
I don’t care too much about analog vs digital, so that wasn’t a factor into my decision. If Elektron ever made a wavetable synth in the analog machines’ form factor I‘d buy it in a heartbeat.
tl;dr it’s sound design and superior performance flexibility that led me to get the analogs.
Also, Dark Trinity sounds a lot cooler than Digi Trinity.