I have to come to the defence of the Jack Russell.
There is/was 2 on my dads street.Friends of my dad.They are both senior owners.Rebas owner is now in a home due to Alz.Daughter took Reba.Reba was the sweetest,calmest dog.You would always see Alice taking Reba for a walk,baggie in hand.Reba loved everyone.And never bothered cats.Ross,who is still on the street,also has a very calm one.Now for the life of me I can never remember the dogs name...LOL.This dog also loves people and has never chased a cat.And loves other dogs.His son has 2 GSD's.The only time this dog goes rangy is in the car.I always got a kick watching him go zoomy in the back seat.Then Ross put him in his crate.There are also 3 JR in my area.Very calm,walking nicely,not hyper.I alway bump into the one owner Andrea when I'm out with Tron.I guess it's all on how you train them.And it seems that all the effert pays off in the end.....
As for the Shih Tzu,here is what I have about them
The role of the companion and household is the sole purpose of the Shih Tzu.Therefore,the personality is outgoing,affectionate,happy and friendly.Intelligent and docile.The breed really attracts admirers.
If I recall,we have a Shih Tzu owner on here.
Also,since he is in a foster home,it's easier to know what his bad/good habits are.This the foster Mom will let the shelter know.