Well, in my opinion, once you start getting into the latest generation of
Boss pedals, with more and more features, you run into these problems:
1. Higher Price
2. Useless features (features that may seem cool at the store, but you get it home and you end up finding NO use for a "reverse delay" or something else like that
3. Cheaper, Metallic sound.
I sat and compared a DD-3 to a DD-6. The DD-6 was more expensive, and had a bunch of silly features. The DD-3 is cheaper, simpler, more straightforward, and has a WARMER tone than the DD-6. Im sure your thinking "what? its DELAY! How could it be 'warm' sounding?" but it really does. The DD-3, to my ears, sounds MUCH more natural. I suggest you try them both out and see for yourself what I mean by the extra warmness. (BTW, I set ALL the controls on the exact same level, feedback, delay length, ect. The DD-6's repeat seem to get harsher and metallic as they go on, where the DD-3's repeats seem to sound very authentic.
As for the chorus, Ive never spent much time with them, so I cant really say much, except that I dont like any of the newer boss pedals, I like the old discontinued models, like the first and second generation of a pedals.