I've never owned or skied either of these boats, but when we were looking for our current boat there was a 205 and a few Echelon's in consideration. Personally I think the Echelon and the late 90's Response's are some of the nicest looking boats on the water but from my memory there are a couple things to watch out for.
The Echelon used an in-dash computer system called "Computron" which was prone to failure. If I remember correctly this system stored and monitored engine vitals along with water and air temp. Pretty sure this was gone by about '96? However, the newer Echelons and a lot of the Response's used a different shaft log setup they called an HDS box which was prone to leaking and difficult to properly fix once the leaking started. I know any boat has its potential issues, but those were a couple that made me lean towards the 205 when we were looking (91-95 hull).