Ah, that makes sense - I was thinking of a standard poodle but I am guessing you were thinking of one of the smaller ones as a standard is quite a big dog?
Poodles are pretty intelligent so you might find one of those needed lifelong mental stimulation, which is a bit like training. I think they often struggle with being left alone, too - though many people do leave theirs succesfully. They are sensitive so require a gentle hand when training.
Schnauzers are quite high energy breeds so you may get one that needs more than an hour a day and they can be suspicious of strangers and pretty independent minded - meaning training can be pretty intense with them. Some can be pretty barky, too.
Havanese can also be noisy and sometimes also struggle with being left alone. I suspect they are the easier of the 3.
I find it can help to think of what the dog's are bred to do.
Poodles are gun retrievers. They need to be quick to learn and often work alongside a single person all day long. This means they can bond to a single person, love day long stimulation and tend to enjoy using their noses and mouths (sniffing and chewing).
Schnauzers are pinschers which were used for pest control and guarding. These are activities that don't require a human so the dogs are independent and tend not to mind time alone too much. It also means they might not be as easy to train because little training was needed fo their work.
Havanese are bichons and were primarily bred as companion dogs. As a result they tend to like people more than other dogs and struggle to be alone because they are bred to love human company so much.
Of course, you are right, all dogs are individuals so your own mileage may vary 