Some foods are almost required to be fresh, they lose so much in quality when canned. Hot Chinese mustard must be mixed up freshly from powder for maximum heat; lemon juice from a plastic lemon is missing the full flavor and aroma of freshly squeezed lemon juice. Of course, some foods that come in jars are great. Chowhounds love Sriracha, or "rooster sauce," a jarred sauce of chile paste, garlic, vinegar, sugar, and salt. But rarely does anyone suggest grinding your own chile paste and mixing it up fresh instead. The jarred stuff is just fine! Thus balancing effort with reward, convenience with quality, is a crucial skill for the home cook. Where on this spectrum, Russel Shank wants to know, does sauce for pad thai lie?
That sauce is elemental and simple, says scubadoo97. The goal is a balance of three strong flavors: salty/funky (from fish sauce), sweet (from palm sugar), and sour (from tamarind and/or lime juice). There are three reasons why, in this case, homemade is leagues better than the jarred stuff.
One, it's incredibly simple to make—just three ingredients, no cooking. Two, the jarred stuff is kind of nasty. "The texture is often too thick, probably due to thickeners and stabilizers," says fmed. Finally, explains fmed, there's the necessity of balance in Thai cuisine: strong flavors together in perfect harmony. Too sweet, or not sour enough, and the balance is all off. And it's unlikely that the perfect balance of flavors for your dish is the one the sauce factory came up with. This is where the homemade version has it over the jarred version: It's infinitely customizable.