Teddy and Jinny, of course squeezing the bag will make ot flow faster, but she said there is a difference INDEPENDENT of height.
Given the same caliber hose and connectors, the closed top bag, if filled to the top, will have the greater flow and pressure as the water flows out of the bag and down the hose.
Here's a lesson in fluid physics. If you want more info, check your Halliday and Resnick text. You do have one, don't you?
1--The solution in the bags we use, unless we pressurize them somehow, all flow into us by gravity. A column of water exerts approximately one pound of pressure for every 27.68 inches of water column height (INCLUDING the water height in the bag).
2--All the air in the tube must be expelled for the water to flow smoothly.
3A--In an OPEN TOP bag, the height of the water column CHANGES (goes down) as the bag empties, hence, the pressure and flow rate when the bag is full, is higher than when it is just about empty. If your bag is 12" tall, the pressure will be about 0.43 psi less than when it was filled to the top. You can see the level of water go down in the bag. (The ambient air in the bag on top of the water does NOT push it down.) This is more noticeable the LOWER you hang your bag.
3B--In a CLOSED TOP bag, if you completely fill it to the top, the height of the water column STAYS THE SAME HEIGHT as the bag empties because no air enters the bag as water flows out and the bag approaches being empty. Therefore, the pressure and flow rate in a closed top bag STAYS THE SAME from the time you first open the clamp until it is empty.
This IS how it works. If you need more explanation, see your Halliday and Resnick.
Having said all that, I prefer the Klystra open top bag because I can use a much larger caliber connector for the tube to the bag than you can use in a closed top bag, where the bore of the connection of the tube to the bag must go through the screw top which is usually quite small, usually about 3/16" I.D. and THAT restricts the flow rate. I recommend that users of the Klystra bags remove the black tube connector and replace it with a nylon connector with a 3/8" I.D. and use at least a 3/8" I.D. hose for good water flow rates. 20 years ago, the Klystra bag had a bigger diameter hose connection than bags made over the last several years. I know this because we have new and older bags.