Each of these types of filter design have their pros and cons.
For instance Polypropylene is a much more sturdy construction so it will usually last longer than pleated filters. String Wound filters work most efficiently for well water because of the surface area they have to capture larger sediment particles. Pleated filters are usually the most economical.
What's more important to look for in deciding on a filter is Will it filter what you're trying to filter out of your water? Is the flow rate enough for your household requirements? Will it fit your current housing? How often does it need to be changed? Are you looking to get rid of Chlorine taste & odor or VOC's? (hint: if you are you'll need a carbon filter)
If any one type did EVERYthing better (including cost), it would eventually push all others off the market. There are many different filter applications. Big dirt, small dirt, gritty dirt, gooshy dirt, uniform size and assorted size, constant or intermittent dirt or flow.
Some filter types work better (filtering/cost) in some applications than in others. In addition to pleated and string, there's coarse screens and fine carbon filters, and probably more types for special uses.
Pleated is filter "paper". Really a blend of selected fibers and binder pressed into a sheet. By adjusting fiber type and density they can make coarse or fine filters. "Paper" filters are WIDELY used, for oil-filters, air-filters, water-filters, and odd applications. (Obviously most applications use water-proof fibers and binders.) Your car uses "paper" filters for its engine air, oil, maybe cabin-air and transmission fluid. Shop-Vacs use paper. HEPA filters on new vacuums are just a very special "paper". Filter stuff is made in many types in huge rolls, then cut and bent into all the different filter sizes and types.
Since the idea is to catch the most dirt in the least space with little drag on the air/water/oil going through, they take maybe 3 feet of paper and fold ("pleat") it to fit in a 1 foot circumference.
Pleated "paper" is usually low-cost and very effective.
String is a roll of twine. It is wound tight on the inside and gapped on the outside. The inside catches the very fine particles, the twine-type selected for the micron size. The more-open outside catches larger stuff before it plugs the fine center. A string filter may be much heavier than a paper filter. It may also stand larger pressure-loss, though that's not significant for most domestic filters (we want low-low pressure loss so we get a nice stream at the tap or shower).
When you compare a half-pound pleated-paper filter to a 3-pound string-wound filter, you say "wow!" String-wound is very substantial. That does not make it better for all uses.
I don't think a simple string-wound filter can be made for very small micron-rating. Paper may be pressed very dense, down to large-germ sizes.
Paper "should" be cheaper than string-wound: they make miles of the stuff, you don't need much per filter, and element fabrication is simple. However, I found that FiltersFast stocks a string-wound which fits my canister for about the same good price as the pleated paper filters I was buying.
I beat-out and re-use some paper filters. When my car lacks pep I beat the air-filter and get back some pep. Similar for the Shop-Vac. Maybe some water-filter users can dry and brush the crud off their paper water filters; my well gives both coarse and fine dirt which packs into the paper and doesn't want to come out. I was changing water filters every month. (Even at FiltersFast's good prices, this was getting costly.)
> Filters are cheap enough to get one of each and experiment.
Yes. That's what I'm doing. I've gone through a dozen paper filters and know how they last. I just got two string-wound filters and so far the first one seems to be holding-up better, for my water condition. When the string filter does get full I'll try paper again, compare life and water quality.
This is not quite fair because I also added a mesh-screen pre-filter to catch the biggest chunks before going to the paper/string filter. (FiltersFast should stock the VU-FLOW 100 and 10 micron in 3/4" and 1" size. The place I found it charged too much and sold me the wrong size.) That's another type of filter, more a trash-screen, and a useful step in some water filtering applications.