Just my opinion, but I make starters for wine, mead, and cider in most cases. In the case of cider the reason is I use ale yeasts and I never do less than a 6 gallon batch so I end up with about 5 gallons. And at the standard pitch rate for ales of 500,000 cells per ml you need about 141 billion cells total which you don't get in a regular dry yeast packet (~55 billion) or a liquid yeast vial (~125 billion average). Of course if you're doing =< 3 gallons a starter wouldn't be necessary. I know most dry yeast packets and liquid yeast vials claim they're enough for 5-6 gallons, and they can be given enough time but you'll have a longer lag time until the yeasts build up enough population. This ain't always bad if you want more fruity esters but you do run the risk of stressing the yeast to where they might put out off flavors depending on the other variables. I don't have much experience making cider so this is just book knowledge from making wine and mead but until I get more trigger time that's what I believe to be true. Also lower temperatures favor a larger yeast population as well or the lag time will increase further, so like in the case of certain ale yeasts, if you ferment them at their optimum temperatures of between 63-68 or so, it's probably better to have a higher population from a starter than if you were fermenting at say 72 or so. Up till now I believe my wines and meads came out better by using starters but until I make two identical batches of cider except use a starter in one but not the other I can't say for sure. I'm going to stick with them until I find out different.
