Recently I've been equivocating with myself over whether I want to buy a matriarch or a KARP 2600 m.
I've rented a matriarch and I liked it but I did feel like it was slightly wanting in girth/punch/phatness/whatever you want to call it compared to the model d, while obviously being more versatile in many ways.
However people often say the 2600 is at least the equal of the minimoog in that regard while having a lot of the same semi modular functionality of the matriarch. The BBD on the matriarch vs the spring reverb on the 2600 is kind of a toss up.
I will say trying to run other synths through the matriarch was somewhat disappointing possible due to running into the excessive filtering when going through the line out. It seems like the arp 2600 is more highly regarded for signal processing.
Of course there's always the "porque no Los dos" option but curious to hear from anyone who has or has had both.