Spring vs worm gear clamps?

The one simple reason manufacturers use spring clamps instead of worm gear clamps:

Cost

It costs far less to mass produce spring clamps and use them than it does worm gear clamps.

As far as your bonus question goes, I would agree with your gut. There is no way a spring clamp is going to clamp any better than a worm gear clamp. You would be able to get the worm gear clamp tighter than a spring clamp, that's for sure. As long as the worm gear clamp doesn't get deformed, you can continue applying force to it and getting it tighter. The spring clamp is still adequate for what it is designed to do, though, or it wouldn't still be in use today. The worm gear clamp would most likely last longer as long as it's made out of stainless steel (as opposed to the cheap aluminum ones I've seen from Harbor Freight). Realistically, though, either type of clamp should last for the life of the car.

Great question. Spring clamps have several advantages from the engineers point of view. They apply even pressure around the joint, screw clamps do not. Screw clamps pull from one side and this can stretch the hose, pulling it to the screw area. In smaller sizes, screw clamps leave a flat spot under the screw fitting; this leaves low pressure areas at the each end of the screw fitting. But most important spring clamps continue to apply pressure as the rubber of the hose dries out and shrinks over time making the joint last much longer without maintenance.

Corrosion can be in an issue for poorly coated spring clamps. Care must be taken to place a clamp back in the same place on an older hose. If not, it can leave a section with little or no pressure and lead to a leak. We switch back to spring clamps whenever we take a hose connection apart. We apply spray silicone lubricant between the clamp and the hose to allow it to slide as it shrinks.

This applies to flat band spring clamps, round wire clamps are a poor choice as they have too small of a pressure surface.

Regular strap clamps do not work as well. It's common to get cold-flow leakage around them whereas the spring clamps work better across the wide range of temperatures. If you have a strap clamp, you end up overtightening them to try and compensate.

Spring style hose clamps are typically fabricated from steel alloy and plated with zinc for corrosion protection. Aluminum would not be a good choice for spring clamps due to low elastic limits and cost. Forming an aluminum spring would also require heat treat and tempering after forming then corrosion protection such as anodizing, all adding more cost. Steel Spring style hose clamps have several advantages over Worm Gear style clamps as they continuously apply the same clamping force under all environmental conditions, over their entire life. With temperatures changes, rubber shrinkage with age, and vibration loads, the spring style clamp consistently applies force to seal the hose. Worm Gear clamps on the other hand can become loose due to vibration, material shrinkage, temperature fluctuation and can be grossly over tightened damaging the hose and radiator fittings. Spring clamps are also much quicker and simpler to install. With the right tool the clamp is expanded and place into position and tightened by simply releasing the clamp. Worm Gear clamps require a way to rotate the worm gear numerous times to tighten and torque limiting method to prevent over tightening. For and assembly line, spring clamps make more sence.
I just replaced all of the hoses on a 22-year-old Honda that someone had put aftermarket hoses on and had to change to worm gear clamps because the hose diameter was larger than the OEM hose. The clamps were so tight that they cut the rubber to the fiber reinforcement layer, not good. Put OEM hoses and original spring clamps back on it, no leaks!

Been researching this because i recently had an experience where the upper radiator hose came loose while i was driving and i was absolutely sure i had tightened down the the "worm gear" clamp properly when i installed the radiator. But apparently the rubber hose had compressed some and the clamp lost its clamping force. Being that the radiator inlet is plastic, I am somewhat worried about applying to much clamping force. I noticed that the original factory clamps were spring clamps. I see now that the advantage of the spring clamp is the constant clamping force even when the hose shrinks or compresses.

All makes sense to me. However, sometimes strang things occur. Hada 2007 avalon with power steering fluid leaking. Been leaking for years and owner was frequently topping it up with cheapo stp psf. Well i could see that the hoses were wet. I replaced all the wire spring clamps with worm roller and over tightened them im sure. Its been a year now and no more top ups. Every case is unique