The besst discussion, in my opinion, on differences between coloplast and AMS is at the following youtube video (done by Dr Kramer from Maryland):
https://www.youtube.com/watch?v=8PPId-OVzagMOST IMPORTANTLY, they explicitly state that the ultimate fully erect size is dependent on the surgeon who chooses the implant . in other words, a 22 CM titan will give a certain length , and the titan pretty much goes to that length and then stops. Think of guys with a Titan as being "showers" and not "growers"
The LGX (LGX = "length girth explansion") has a cool mesh design which simulates a natural penis length increase when the cylinder is pumped up. The key point is that a 21 cm LGX will "max out " at 21 cm. When deflated, It will start shorter (thus my point about LGX sort of simulating a guy who is a "grower"). I suppose, a really skilled surgeon might feel comfortable "oversizing" an LGX, and in turn, that might lead to lengthening; but, the video directly addresses this point and says that the length is a function of the surgeon's technique, and NOT the implant.