A lot of people call HFM bloated, with useless additions like the countries of Andorra, Monaco, etc, and other things.
But what gave me the biggest push to favor it over HPM is how there is an English, Scottish and Welsh cultures there.
Not even a Britton myself, and have no particular love for it, but I have always found it very, very odd how Vic2 only had a basic British culture.
There's an option to get rid of microstates and such. I ended up liking it for playing as European majors/the United States, but HPM for other nations since you get fewer of the scripted colonial events screwing you over.