Actually, we went through the exact same experience. We got Winston first, and he is perfect. Potty training was a breeze. He never chew or mess with anything other than his toys. You never have to yell or fuss at him. Then my husband wanted his very own Daddy's Girl, hence Maggie. I tell you if she wasn't so cute, we'd killed her already.
Potty training was the awful, we even worked with a trainer. It was a never ending battle until a couple of weeks ago, she just turned one yesterday. She has now learnt to ring the bell to go out. So remember, there is an end to your situation. Winston didn't like her one bit at the beginning. He never realized that he was a dog until we got Maggie. It took him almost a month to warm up to the idea that she is here to stay. Now they are inseparable.