The only Newf I've met was raised by ass hole owners who shouldn't own a dog, particularly a 200 pound breed. The dog was known to charge up to strange dogs dragging the owner behind him. Even when the owner finally had control over him she didn't and the dog was allowed to sniff everyone. I was reprimanded several times when my dog aggressive dog went after the Newfie after it stuck it's nose up my dog's ass AFTER I told the owner to keep the dog back a foot or so. while they are sweet dogs they are not for everyone.

I've never met a bad Chi though. I've been around a lot of dogs but every Chi I have met was well behaved. One was a little barky but that is common in toy breeds, particularly when they are left alone for a long time on the bench. It depends on how you socialize them, you have to go into it treating them like a dog not a child.