It's absurd to compare Valeska and Turis based on the matchup between cavalry and archers :D. Here, we need to evaluate who is more useful at the start. Obviously, Valeska will often have more archers at the beginning than any other hero. Since the early game revolves around archers, people choose Valeska (not to mention that ranged attacks are significantly stronger). That's the whole logic. Turis has her own advantages, as her tactics allow her to easily overcome ranged defenses, and a stack of spearmen also helps. There's also the hero Orrin, who shouldn't be forgotten. And of course, Caitlin.