I have family members who send their kids to both those schools & they are both extremely happy. The child that goes to Heathdale commutes from Point Cook. They get a lot of homework at Heathdale compared to Seabrook & even compared to my own kids who are at a catholic primary school. As for other schools in Hoppers, unless you are in their zone there is no way you would be able to get into the more sought after ones unfortunately.
I have heard good things about the catholic primary schools in Point Cook & have a friend who teaches at Stella Maris who is a fantastic teacher & sends her own children to the school. I have other close friends with children at Westbourne who are happy, one in particular raves about the junior campus at Williamstown.
Good luck with your decision, I am currently 'school shopping' for my DS as I don't think my girls school will suit his needs, but dislike the public school we are zoned for & have no chance of getting into my school of choice for him due to it being zoned and capped

You would also need to be in the zone to be considered for Seabrook apparently, so that may be something you have to look into.