Differences between "would" and "used to" when we are talking about habit

Question

What is the differences between use "would" vs "used to"

I used to play football when I was a child.

I would play football when I was a child.

Answer 1

Would is usually restricted to actions performed on specific occasions or under specific circumstances; it virtually always requires a modifier identifying these.

Whenever I had trouble with schoolwork I would ask my friend Henry for help.
If I wanted to be by myself I would go to the park.
My parents used to read to me at bedtime.

Used to is employed for these, too, but it is also employed for actions performed without any sort of circumstantial specification, only a timespan locative:

^OKI used to play football.
^OKI used to play football when I was a kid.

Would is not usually employed for these:

^∗ I would play football.
^? I would play football when I was a kid.

However, this restriction may not apply if the circumstantial specification can be inferred from the discourse context.

A: What did you do if you needed help?
B: Oh, ^OKI would ask my friend Henry.

Answer 2

"Used to" expresses something done or habituated. (See definition in Oxford).

"Would" expresses a desire or intent, and is the past tense of "will". (See definition in Oxford).

"I used to play football when I was a child." can be re-expressed as "When I was a child, I played football"

"I would play football when I was a child" can be re-expressed as "When I was a child I had a desire to play football."

Obviously, if I played football as a child because of a desire, both forms of re-expression can be true.

By a literal interpretation, however, saying "I used to play football" can mean having played without any wish or desire to. In comparison, saying "I would play football" expresses a desire, with no claim of having actually played.

Obviously other qualifications affect the interpretation. But, without adornment ....

(Edited to add links following request).