There are times where I would tend to favor one over the other, but I'm having trouble figuring out a simple rule that dictates which one I would choose. I would describe:
- The aroma of bread, coffee, and wine, but
- The scent of a skunk, a perfume, a flower, or a woman
Aroma seems to be the more natural word for describing blends of food and spice, while scent seems to be more apt for describing the natural smell of a plant or animal.
Also, not too unlike atoms and molecules, scents seem more fundamental, while aromas seem like more of a mixture or blend. So, I might talk about the scent of a particular candle, but the aromas of the candle store.
Still, the literature has plenty of counterexamples, such as the scent of bread, or the aroma of the flower, or the scent of the wine, so it would be a mistake to interpret any of these thoughts as "rules". The two words are largely synonymous, so there's plenty of room for overlap. If someone said that only one of the two words could be used in a particular context, I'd regard that as smelling fishy.
As indicated by narx's answer to a similar question on ELU (English Language & Usage, ELL's "sister site" aimed primarily at linguists, etymologists, and serious English language enthusiasts), only little can be used as an unqualified noun to mean a small amount (where adjectival small needs an explicit noun, such as amount or quantity).
The other interesting point made about little there is that in...
1: I have a little experience teaching English.
2: I have little experience teaching English.
...the two sentences have almost opposite meanings - #1 implies you have at least some experience, whereas #2 implies very little (perhaps almost none). In fact, #1 is often used somewhat facetiously to imply you actually have a lot of whatever is being spoken of.
Apart from the above distinctions, there's also (as kiamlaluno points out) the fact that little often carries more "affectionate" connotations than small. And from BBC Learning English, little is more common in the sense not much when coupled with abstract nouns such as hope, chance, change, effect, use and point.
In most other contexts, there's little to choose between the two words. Use whichever you like.
Best Answer
'Few' is mainly used when talking about the number of 'count nouns', such as 'dogs'. You can say
to mean that not many dogs make good friends with cats. But if you said
this would suggest that dogs that are small (cat-sized, perhaps?) make good friends with cats.
On the other hand, 'little' is used when talking about the amount of 'mass nouns', such as 'water'.
means that not a lot of water got into the house (thank goodness!). On the other hand,
is not a valid sentence.
Sometimes you can use either to produce equivalent sentences, but usually 'few' will precede a plural noun and 'little' will proceed a singular (mass) noun. For example:
Both of these sentences mean that they haven't given the other much cause to dislike them.
A little and a few both mean some, but the above rules still apply here. So you would say a few dogs and a little water, but not a little dogs or a few water (which aren't valid sentences).