Spells are specific, get you what you want. Rituals can sometimes encompass spells depending upon the intent of the ritual. However, sometimes rituals can serve other purposes or many purposes- communing with the Gods/Goddess and ancestors and fey, celebration, thanks, or a good old fashioned party of sorts. It's all about the intention. The best part about rituals? No sin, no sermon, no guilt, no barganing for a little something good. If you want something, make it happen, all things are possible.
And by the way, this is just my opinion. Witches have a variety and often times contradictory number of views on the subject.