Ok, this is a very simple concept. People all the time ask "which gun is better" or "which gun will win" or the such. However, it it not really correct to compare two guns and try to decide which one would "win" unless user skill is defined in that situation.
A gun is only as good as its user. Never forget that. A n00b wielding a big gun like a CPS 1500 can be driven back by a seasoned veteran wielding a small gun like an XP 310. In the same way, two users to equal skill with guns such as a 1500 vs a 2500 will balance each other perfectly. These are not based off logic, these are based off actual observations. Little is more threatening than a user who knows how to use his/her gun effectively.
A good user maximizes his gun's strengths. That is obvious. If your gun has amazing capacity, go on the offensive and shoot often, get the pressure on the enemy, make things hot. If your gun has amazing range, get on the front lines and hammer the enemy from afar, but only take well placed shots and in the tap-pump style unless your gun also has the capacity to justify taking lots of shots. Not using your gun to its fullest ability is like going out on the track during a meet and jogging the 100m dash. If you want to win, you've got to use the strengths of your gun against the enemy but also against the enemy's counters. A competent enemy will try and negate your gun's strengths and you have to be ready for that. Don't get drawn into bad fighting places and don't assume the enemy will do things they obviously won't, like attacking a heavily fortified hill head-on.
A good user cancels out his gun's weaknesses. Like my "Elimination of Capacity Stats" article I will be writing. If you are using a gun that guzzles water, such as a CPS 2000, don't let the enemy play off that weakness! Eliminate it! Using the tap-pump method, you can eliminate any disadvantages in shot time and shots per tank. That way, you can stretch your tank out for over an hour and never get anywhere close to running out of pressure. Ever. You should never run out of pressure in a non-soakfest war ever again after reading that upcoming article. In a similar way, if you have a CPS 2100 and are facing longer range guns, don't let the enemy use that to their advantage. Fight in places where range advantage is negated. There are few places where range doesn't help, but there are places. And I won't say where to look, since my opponents read the iSoaker forums too. :p Also, don't forget to counter your enemy's counter against your counter! Water warfare is as much a psychological game as a physical showdown. Every move has an effective counter, and every counter has a counter! You will need to do a lot more in order to draw an enemy into an ambush spot, out of a fortification, or down from a hill. Have patience, always keep your disadvantages down, no matter how you have to lure the enemy into your grasp.
Lots of newbies with bad guns vs a handful of vets with good ones: This is an old debate, and in this situation, the battle could swing either way depending on the terrain and how severe the gap is. However, no matter how powerful your guns, or how many years of experience you have, there will be situations where inferior-armed enemies will overwhelm you purely by numbers. It happened to me as recently as the last war! I can take on 3 at once, but as that battle showed, 4 is too many. When the better armed soldiers have the numbers advantage there is no excuse for defeat! [Well there is, but that's the subject of yet another article]
Every user is different. Just because someone with a CPS 4100 fights badly doesn't mean every 4100 user fights badly. In the inverse, not every 2500 user will be like the guy who just kicked your ass today. So, you have to treat each user independently and form a strategy against that person as an individual. Each time the person behind the gun changes, you have to change too. One strategy will not work against every user of a certain soaker. Switch up your tactics and make them appropriate for the enemies you are fighting.