I would eat well when I was a child.
I used to eat well when I was a child.
Is there any difference in the meaning between these two sentences.
I would eat well when I was a child.
I used to eat well when I was a child.
Is there any difference in the meaning between these two sentences.
The only difference, according to me, is that the second sentence means that you don't eat well in the present time, while the first one says no such thing.
The first one sounds unnatural to me, something like "If I was a child, I would be eating well", while the second conveys the message "I ate well when I was a child, but I don't anymore" This is because used to refers to something that happened before, but currently doesn't.
Personally, I would say:
I ate well when I was a child
I would eat well when I was a child.
I used to eat well when I was a child.
Both sentences are correct and have the same meaning.
"Would" is used as part of conditional constructions - but not solely there. Its other uses include:
On the last point, Thomson and Martinet's A Practical English Grammar (Oxford University Press, 1986) gives this example:
Bill objects (or objected).
He would! or He would object! (= He always objects.)
In this idiom, the word "would" is stressed.
Thomson and Martinet say that, whereas "will" is only rarely used to express habitual action (An Englishman will usually show you the way in the street), "would" has a wide application to past habitual actions and is generally equivalent to "used to". On the distinction between "would" and "used to", they contend that when "used to" is used to describe a "discontinued habit" (as in "he used to drink beer, but now he drinks wine"), "would" cannot replace "used to".
I don't find OP's first example idiomatic, but some people might accept it. Note that used to can be used to refer to past circumstances as well as habitual actions...
She used to be fat
...which we can't express as She would be fat. It's not the same as She would visit me = She used to visit me.
So far as I'm concerned, eating well is like being fat - they're "continuous states", which can be referenced using used to be, but not would.
Perhaps if you think of eating well as something you might do from time to time (We would visit my grandparents, where we always ate well), you might accept OP's first example. I can't really go along with that, though.