what's the difference?
I dont think i've ever had Tostitos...
The main difference is that Tostitos are much closer to just being a straight tortilla chip: the only flavor variation (not counting different sizes/shapes or multigrain vs. corn) is lime; with Doritos, the flavoring is the centerpiece: nacho cheese, cool ranch, spicy buffalo, jalapeno, etc. All somewhat aggressive flavors when compared to lime or unflavored. I believe that Tostitos generally use a higher quality corn (because they're not using a possibly overbearing spice to cover up the corn).
The end effect is that Doritos work much better than Tostitos on their own, without a sauce or dip (indeed, the only dip that I've found to work at all with most (not all) Doritos is sour cream... salsa tends to get overpowered by the Doritos and nacho cheese doesn't work that well either), while Tostitos practically require a dip, as they're even blander than plain potato crisps or Fritos (which in turn means that any of the three dips/sauces I listed earlier works fantastically with Tostitos, IMO).
From these threads, it appears that none of the three dips listed have wide availability in the UK, and I suspect that's why PepsiCo has made no effort to bring Tostitos over.
