Pros and cons to each cage.

CB6000s

Pros:

Tucks neatly under most clothing. Virtually unnoticeable even in tighter street clothes.

Comfortable. Once the correct ring and pin is selected, you all but forget that it's there.

Cons:

Hygiene is more particular. Areas that are difficult to get to do not clean as easily, and parts that are completely covered do not dry out. This leaves the skin moist all the time and softens the skin to the point that it is easily abraded.
----

CB-Curve

Pros:

For the average guy, it is much more comfortable due to its size and length. The same applies to ring size and pin length as far as overall comfort.

The more open design of the cage portion allows for more thorough cleaning and drying which helps protect the skin.

Cons:

The biggest drawback to the Curve is also its biggest asset.... Size. While it may be more comfortable to wear along with being easier to maintain cleanliness, it doesn't mask very well under tighter clothes.

Both units lend themselves to what I call "lock knock". Vigorous activities and certain movements can cause the lock to bang against the cage. This noise may be more perceived to the wearer than noticed by others. This can be easily addressed by using one of those elastic bands that ladies use to pull their hair back. Double the band over the cage and pull it up over the lock. No more lock bounce, and not noticeable to the wearer.
The thickness and width of the rings is an unavoidable consequence. Because of the material used (acrylic) the rings have to be considerably larger than the metal counterparts. In my opinion, the ring is the least comfortable part of the whole set up.