So I just got a digitone and have had a model: cycles since around the time it came out. The model: cycles was my first elektron product and I have since gotten a digitakt and a digitone.
The workflow for crafting a sound is completely different, and I think it is easier to make tonal sounds on the digitone than percussive, whereas I the cycles can instantly make good precussive sounds. The sound sculpting is much more in depth on the digitone, in fact I think the digitone rivals my modular when it comes to customizing a sound.
As far as retrig goes, it has the arp which you can use in very similar ways. In fact I find the arp to be much more powerful. The primary difference is that the arp is on or off and when you press a key the arp pattern starts rather than having to hold the retrig button. You can almost treat the arpeggiator as a sequencer you can trigger by pressing the keys. It can have different note patterns with some notes on or off for rythmic patterns, it is very configurable.
The effect send amounts are p lockable, which I generally find to be enough since you can change the effect parameters on a per pattern basis, so you can change your effects going from one pattern to the next. Also if you have something that can sequence midi ccs (a digitakt, or possibly digitone midi into itself) you can sequence the effect parameters with ccs.
I find the two devices to be a very good pair. The cycles can make great drum sounds very quickly and the digitone can make highly tweakable tonal sounds. Obviously there is significant crossover, but they each have their niche. Also I find it hard to get a really good snare sound on the cycles and there is a fantastic one on the digitone.
EDIT: Also there is a significant difference tonally between the devices. The digitone can do amazing ambient pads and evolving sounds that is very hard to do on the cycles. Having a filter on all the sounds is also very nice. I just wish there was a filter for the incoming audio. You could have some amazing dub fun with that.