
Range: The Colossus outshoots the Colossus 2 on every nozzle. The difference is not much on N3 and N9, which they both share. It is significant on N7 vs N5, greater than 4 feet for sure and maybe as much as 7 feet. It is too cold and windy to attempt measured ranges right now. The margin of difference on several shots was taller than I am, I can say that though.
Output: As mentioned above, the downgrade from N7 to N5 is a big step down, not a small one as it looks on paper.
Shot Time: The Colossus has longer shot time than the Colossus 2, owing to its larger PC. Much more of the stream comes out at high power with the original. The Colossus 2's peak power is good, but does not last very long, forcing the user to pump frequently. This is noticeable even on the N3 nozzle.
Pumping: The Colossus 2's PRV does not freak out like the original's when you hit high pressure. However, its pump is considerably louder and stiffer. The difference in pumping noise is one of the most striking differences between these two models. The pump handle on the Colossus 2 offers less grip for users with larger hands. Pump volume appears to be similar if not the same.
Reservoir: If the Colossus 2 holds less water, it certainly doesn't show it. The reservoir is large and feels more sturdy than the original. It outlasts the Colossus when shooting N5 vs N7, although that's to be expected. The Colossus 2 is harder to fill in a shallow sink, but the cap is better placed, so you can easily fill the whole reservoir.
Nozzles: Note that the nozzle plate is inverted on the Colossus 2. If you memorized the order of nozzles on the Colossus, you will need to relearn it for the 2.
Special Features: The "Angle Meter" on the 2 is actually useful. Not on that gun, as its side placement makes it hard to see, but to help correct your aim on other guns. The angle meter may end up being the most useful part of the whole blaster as it is now possible to accurately line up guns to the sweet spot when testing. No more guessing or trying to rig things to help with the angle. Simply take it out of the 2 and attach it to the gun you want to test. The Python 2 also ships with an angle meter in it and would be a cheaper source of these things.
Size: The Colossus and Colossus 2 are essentially the same size. The 2 is a little bit taller and the original is a little bit longer. The boxes are almost identical in length and width, a point proven when both are examined in person. In pictures, the 2's box looks smaller, as Buzz Bee has found ways to reduce cardboard.
Balance: Because of the extended casing, the Colossus 2 feels better balanced than the original. The reservoir doesn't jiggle around as much and the body does not taper as much vertically.
Look and Feel: The Colossus 2 repeats much of the original color scheme, but the black reservoir and new sticker style give it a more serious vibe than the original. The 2's reservoir joins the Raven as the most badass looking reservoirs among all water guns, imo. The 2 has a support that joins the pistol grip and bottom reservoir support. This essentially acts like a stock, making it comfortable to fire. The 2 feels much more solid than the original due to casing enclosing more of the PC and reservoir. However, some of the casing is unnecessary and a step back toward pre-Colossus Buzz Bee models. The pump area is noticeably larger than the original and the casing over the top of the PC in the 2 would be just part of the PC in the original. Why the PC had to be cased over and shrunken accordingly, with a less efficient pump area supporting that smaller PC, is a huge mystery to me. Finally, the 2 has a more angular, geometry feel than the original. There are 7 trapezoids in the design. The original has a smooth, rolling feel, with horizontal and vertical curves.
The Verdict: The Colossus 2 improves upon the design of the original, with a more sturdy feel all-around. It looks more hardcore and easily outperforms everything in Hasbro's 2013 lineup. However, if you are primarily after performance, stay with your original Colossus or Gorgon. If two users of equal skill came to a duel, with all else held equal, the Colossus user would be expected to hit the Colossus 2 user more often. The original has superior range and shot time, with better stealth capabilities and similar field life. The Colossus 2 can definitely take on the original, but its peak power is short lived in comparison. This is a matchup where usable shot time would really make itself felt, a big deal when it comes to air pressure guns. CPS can get away with brief shot times, but air pressure guns need a good showing above 70% range. This is where the Colossus 2 really falls short (pun intended).
Keep your original Colossus!