I also own both, my advice is this, if you are a hardcore player out every weekend and doesn't like to do any smith work get the Systema, mine has been flawless since I got it about 2 years ago. The Celcius... I have had to tinker with it, but its less than half the cost, when it functions it works almost as well as the PTW, I have replaced the electronics with a Systema up kit cost 330.00 plus cost of CTW 620.00= 950.00 still less than the cost of a PTW, if the gearbox goes Airsoft Extreme sells(sold out) the complete gearbox for 275.00, plus 950.00=1255.00 still less than a new PTW with money left over for at least an extra cylinder. The CTW has many flaws, at least the early ones, so be careful if buying used as I have, many of the early ones the paint flakes off easily and the electronics fail, the later have great improvements in both these areas, all have the same hop up as a PTW so the suffer the same vagueness as a PTW but both out perform any of my AEG's. Just my 2 cents.