I found two comparisons of the results from the ZSI 375 and the AMS 800 here and here. There are quite a few more references to the ZSI 375 all showing much the same level of performance as the AMS 800. The second link above has a couple of pictures showing the components of each AUS.
Although I have an AMS 800, please note that I don't have any relationship to, or interest in Boston Scientific, and I am in no way a medical expert so please don't take anything I say as a recommendation or otherwise!
Just looking at the ZSI 375, I can see the advantage of having the opportunity for post-operative adjustment. The AMS 800 is a one-shot job and can't be altered without invasive surgery, so depends heavily on the skill and experience of the surgeon. The ZSI 375 discussions highlight the lack of a need for an abdominal incision for the reservoir, but it does need two incisions around the scrotum for the implant. Personally I found the abdominal incision far less painful than the scrotum incision after the operation. Also, the ZSI 375, is a big chunk of stuff to have in the scrotum. With the AMS 800, I only have the pump unit there - it is a very small, if rather slippery unit. It is not mentioned in any of the documentation that I read, but does the ZSI 375 need a removal of a testicle to make space for the pump and reservoir? Looking at the pictures in the second link above gives a comparison of the relative sizes of the components.
Fingers crossed, my AMS 800 is continuing to work well. It is not perfect, but is considerably better than the virtual free flow I was experiencing before its insertion.
I can't comment on the ATOMS sling. I had a non-adjustable sling implanted (because I thought my level of incontinence was not too bad at the time - on reflection I should have gone straight for the AUS). It worked well for six months or so, but then, progressively, began to have less and less of an effect.
Hope this helps!