Both “would” and “used to” can be used to speak about an activity that someone did regularly long time ago:
Every Sunday, I would go jogging.
The sentences above mean basically the same. However, there is an important difference between “used to” and “would”; while “used to” can be used to speak about past states, “would” cannot:
(The latter sentence would only make sense if you periodically moved from and to London and would require further context for clarification.) This includes also states of mind:
There is also another important difference: “would” can only be used when it is clear that you are speaking (or writing) about something that happened in the past by the time you get to it in a sentence. In our first example, the combination of “Every Sunday” and “would” makes it clear that we speak about the past, since the conditional wouldn’t make sense here. Similarly, we can say both:
When I was a student, I used to go to a lot of parties.
When the order of “when I was a student” and the rest of the sentence is reversed, using “would” is not appropriate because it would likely be misunderstood as the conditional: