When kids pee in cloth, they KNOW they've peed. It's not comfortable, so they get "negative reinforcement" when they miss a chance to use the toilet. It helps them remember "ick, this feels yucky. I'd better use the potty next time!" Of course, kids who have been in cloth diapers all along may not mind the damp feeling anyway.
When kids pee in disposable diapers, it hardly feels like they've even peed. There is NO incentive to use the toilet on time, because there are no consequences to forgetting. And this is especially true for a child who's been in cloth- suddenly, it's even MORE comfortable to pee in their pants than it's been all along! Why go ahead and use the toilet? About the only advantage to sposie trainers is that they're not too bulky or "sticky" when wet, and kids can easily pull them down and back up to use the toilet even if they've already had one accident that day. Damp cloth trainers (or damp cloth diapers that are loose enough to pull up and down, such as the side-snapping fitteds I had for DS) are hard to maneuver when wet.
None of my kids toilet trained until I stopped putting them in any kind of "trainer" and I put them in "big kid underwear." Pull ups and cloth trainers were just too much like diapers for my kids to feel any significant discomfort when wearing them wet. I also have friends who PLed by taking the diaper off at potty time and putting it back on (clean and dry) after potty time, and then after a while switched to underwear, never using any kind of training pants whatsoever.
I also started them using the toilet when they were still using diapers most of the time. Typically, I'd sit the child on the toilet (with potty seat) after undressing before a bath. Then they'd get a fresh diaper back on when it was time to get dressed again. Sometimes they'd pee in it, sometimes not, but it established the routine without any "potty training" pressure.
