I've thankfully not had a bad experience with Mouser, they're generally just fine for us. I do spend a bit more than OP though, so maybe we're in a different service bracket.
I used to prefer Mouser because I thought their site was slightly easier on the eyes, and I felt they were basically interchangeable with Digikey.
A few years ago, I needed about 60 of a very specific, shouldered washer that only Digikey had. It was Friday afternoon and I needed it in Boston ASAP.
I called their support for the first time, with low expectations.
Within a couple hours, they were prepared to put a man from their warehouse on a plane to personally fly these parts to the nearest airport. It wound up being too expensive for the project, but their facility leadership burned multiple hours trying to help solve this problem for me, and I was a very small customer at the time.
After that experience, Digikey gets the lion's share of my orders, which have grown considerably over the years, and they continue to have incredible support, every single time.
They are our first place supplier and we only use alternatives if there is a stock issue, or the price difference is massive.
I've had other vendors try to tell me that Digikey charges too much. But when I get those same vendors to price our BOMs, Digikey is less expensive, has more stock and is far more efficient (e.g., I don't have to call and wait days to place an order and I don't have to order a lifetime supply of everything).
I heard the CEO on a podcast (Adafruit or Pick Place Podcast?) maybe last year sometime, and he
came off as a genuine, nice human being.
Unless they somehow flip 180 degrees, Digikey has earned my business.