The Classics can let all sorts of stuff in if you are walking in loose material (sand and small stones/gravel).
The KSOs don't let rocks in, but can let sand in. You have to cinch them up tight to keep most beach sand out.
The Flows should be the best at keeping everything out, but are hot to wear in summer.
I wear my KSOs everyday to work and it doesn't take me much longer to put them on than the classics. They are a size or two too large though...
The "Seven Deadly Sins"
• Grains (wheat/rice/oats etc) . . . . . • Dairy (milk/yogurt/butter/cheese etc) . . . . .• Nightshades (peppers/tomato/eggplant etc)
• Tubers (potato/arrowroot etc) . . . • Modernly palatable (cashews/olives etc) . . . • Refined foods (salt/sugars etc )
• Legumes (soy/beans/peas etc)