Hi...i would be interested in hearing what you think if you get a chance to hear them/compare them.
I have not heard either, but i have owned CJ pres for over a dozen years straight, and know many friends who own CJ incl Prem 16, 17, ART 1, 2, 3 and GAT. I am fortunate to have found GAT at demo price, and so know it quite well.
Having understood the ET3 is quite close to GAT at much less cost, and Prem 17 is below Prem 16 which is below ART...i would guess that might well bode in the favor of the ET3. Why? because i know at least 3 people who own GAT who also owned ART 3...and unanimously said the GAT is far superior.
I would actually ask how well the ET3 would compete with the original ART 1.
AGain, this is all conjecture based on experience with CJ, owning GAT and knowing a number of people who have owned 16, 17, ART and GAT.
i also noted no one else had responded, and thought at least it might give you some food for thought while you wait for others to respond. Good luck and pls post if you compare them.