Is there any difference between "was always doing something" & "would always do something"?

Question

This is an very interesting grammar point.

I just want to know how native speakers think about this.

The Past Continuous with words such as "always" or "constantly" expresses the idea that something irritating or shocking often happened in the past. The concept is very similar to the expression "used to" but with negative emotion. Remember to put the words "always" or "constantly" between "be" and "verb+ing." Source

Examples:

She was always coming to class late.

He was constantly talking. He annoyed everyone.

I didn't like them because they were always complaining.

Like "used to" and Simple Past, "would always" expresses the idea that something was an old habit which stopped in the past. It says that an action was often repeated in the past, but it is not usually done now. Unlike "used to" and Simple Past, "would always" suggests that someone willingly acted that way and sometimes expresses annoyance or amusement at the habit. It also often suggests the habit was extreme. To express the opposite idea, we can say "would never" to indicate that someone never did something in the past, but now they do. Source

Examples:

She would always send me strange birthday gifts.

Sam and Mary would always choose the most exotic vacation destinations.

Sally would not always arrive early to class. She came late once or twice.

Ned would always show up at our house without calling first.

Mindy would not always walk to school. Sometimes, she took the bus.

Christine would always come late to the meetings.

Jeff would never pay for drinks when we went out together with our friends.

My question is that: is there any difference between "was always doing something" & "would always do something"?

Answer 1

Native speaker here – American English (New England, Boston area).

I may be grasping at phantoms here, but I have a very faint impression that when one uses "would always", it implies "on those occasions on which that person would do this thing, they always elected to do it in the following way", while, in contrast, "was always" implies that the person (or thing) so described was multiplying occasions to do the thing.

That is, using your examples,

She would always send me strange birthday gifts.

Suggests to me that on the occasion of your birthday, she could be relied upon to choose gifts that were strange, while

She was always sending me strange birthday gifts.

would suggest that she wasn't waiting for your birthday to send those strange dirthday gifts!

Likewise,

Sam and Mary would always choose the most exotic vacation destinations.

suggests that Sam and Mary's vacation destination choices were consistently exotic, while

Sam and Mary were always choosing the most exotic vacation destinations.

suggests that Sam and Mary have a very, very busy vacation calendar.

This

Ned would always show up at our house without calling first.

suggests that it was Ned's custom to drop by without calling first, while

Ned was always showing up at our house without calling first.

suggests Ned is making a serious nuisance of himself by imposing on us so very frequently. (Note that in this example, the "was always" formulation has a much strong negative valence than the comparative "would always.)

The difference, I think, is that used this was "was always" is hyperbole, while "would always" is merely a generalization.

Your description of "was always" + verb as implying a negative is correct, but it doesn't explain how that works. It is using hyperbole, which is a figure of speech which conveys valence by exaggeration. When someone says of someone "he was always doing that thing!" it is not usually meant literally; it is meant as exaggeration for effect.

In contrast, "would always" may well be meant literally, or close to literally. When somebody says "he would always do that thing!" they may well mean "whenever he did a thing, it would be that thing!"

By way of illustration: I had a friend who would always be late to parties. Famously so. Like, numerous times he arrived at parties when the last of the rest of the guests were saying good-bye to the hosts. Once, story has it, he showed up the day after the party. Yet I wouldn't say of him that he was always being late to parties because he didn't go to parties all that often. It wasn't like his life was full of party-going, only late. But, by gum, when he went to parties, he would be late; you could bank on it. So my saying of him that he would always be late to parties was perfectly, incontestably, literally true.