We visited Brussels for the first time this year, flying in via AMS and training it.

In doing prep for our trip, we read that the train stations and area around them were pretty seedy. We only used Midi station and yup, it seemed somewhat seedy; particularly at night of course. That said I think when we researched our previously trip to Europe, the reviews for nearly all cities (Madrid, Rome, Paris, etc) indicated you had to be on alert around the train stations and subways.

As a response to the friendliness in Amsterdam and Brussels, as a Canadian, I personally felt pretty welcome while in Amsterdam. We didn't spend enough time in Brussels get a good feel of the vibes but we didn't feel unwelcome.
When we were travelling in Florence and shared a table for lunch with someone from Amsterdam, she invited us to go visit her home when our journey stopped through Amsterdam. We didn't take her up on her offer though. It was kind of a little "too friendly" for us. [Come on, we only got to know this person for 20 mins while eating lasagna. ]