Lays vs Pringles
Pringles and Lay's are actually two different categories of snack food. While Lay's are a conventional chip made of sliced potatoes deep-fried in oil, Pringles are actually potato crisps composed of potato flakes, filters, fillers, and products. In other words, a home chef could never create a Pringles chip at home, but could easily make a Lay's type of chip.
Because of this, the Lay's chip will always have more variability in the realms of appearance, flavor, and texture, whereas Pringles are pretty much the same from canister to canister.
 The Difference in Appearance
Since Pringles and Lay's are so different in substance, they share practically no common ground as far as appearance is concerned.
Lay's chips are simply sliced potatoes dropped in oil and salted (or seasoned, depending on the variety). Therefore, they twist, turn, brown, and caramelize in the hot grease. No chip looks the same as another.
On the other hand, Pringles are far from random. According to Proctor and Gamble's Pringles FAQ, "dried potatoes and other ingredients are mixed into a dough, which is rolled flat and individual discs are cut and placed in a specially shaped carrier which are then taken through the fryer. They are then seasoned, stacked, and packed. the whole process is fully automated." These are the chips you want if randomness isn't desired.
 Flavor Differences Between the Chips
Pringles are the chip to eat if you want a uniform snacking experience with no surprises. Since the chips come from uniform batches of dough, they all taste the same. The texture is a bit mealy; it's obvious that something else is mixed in with the potato, but it's pleasant to the palate. They're also salted and flavored on the top side only, making it simple to change the concentration of spices during the eating experience.
Lay's, meanwhile, are quite random. They're a great deal more greasy than Pringles and have a toasty taste. There are chips with bubbles, sour green spots, and burnt sections. No chip tastes like the others - the most uniform chip in the Lay's line is Ruffles, but even that brand still shows variation. However, it's obvious that one is eating a potato, not an amalgamation of such.
These days, both brands boast an extensive line of flavors and cooking methods to entice a wider variety of customers. Both Pringles and Lay's manufacture low- and no-fat potato chips. Lay's now produces its own line of crisps called Stax, which has a recipe similar to Pringles. Both lines have ridged chips that are marketed toward those who like chips and dip, as well.
The Lay's spread of cooking methods wins; they offer original, kettle-cooked, and baked varieties. Pringles, meanwhile, has a huge list of flavors that Lay's doesn't, with some cross-over. A consumer looking for a range of tastes due to cooking methods will probably like Lay's best, while one seeking interesting flavors would be best served with Pringles.