The difference between WOULD and USED TO

Used to and would are both use to describe something that happened in the past but doesn’t happen any longer.

I used to drink soda, but I quit last year.
I would drink soda whenever I was thirty.

The first difference is that WOULD should not be used unless it has the time frame in the past. (USED TO does require)

I used to watch soap operas every day when I was a teenager.

However, when used to is replaced with would, the same example becomes awkward and ungrammatical:

I would watch soap operad every when I was a teenager.

Try establishing the past before would.

When I was a teenager, I would watch soap operas every day.

The second difference is that WOULD is not used with verbs such as love, be, understand, and feel.

When I was a teenager, I used to love watching soap operas. (Ok)

When I was a teenager, I would love watching soap operad. (Not ok)

PAY ATTENTION!
WOULD is more restricted to use so
when not sure, choose USED TO.