So my philosophy in brewing is to each his (or her!) own, and I recognize fine brews can be made in many, many ways.
But personally, I like tradition, and have strong if sometimes irrational feelings about doing it "right," which usually has some connection to my perception of "traditional" or "old-fashioned." So I'm making my first three batches out of unfiltered cider -- admittedly pasteurized, but then, old recipes sometimes talked about boiling/heating the apples. And of course, I'm adding commercially cultured homebrewing yeast; but then, this isn't a decades-old working farmstead, and I can scarcely expect a beneficial mix of wild yeasts.
So if I were to add sugar in a future batch, it would be brown sugar, maybe molasses or most likely honey. Apple concentrate? Never -- too modern.
Now imagine my surprise when, reading up on cidermaking, I discover that colonial Americans used something called "boiled cider" -- essentially, cider reduced down to a quarter or so of the original volume, and often added to increase fermentable sugars. Sounds a lot like concentrate to me -- and like I may have to learn to be less snooty.
Now splenda on the other hand ...