Should We Get A Puppy?

Hello, About a month ago we sadly had our dog put to sleep. We are now ready to get another one. Unfortunately we cant decide if we should get a puppy or an older dog and have been a logger heads ever since. Myself and my partner both work 9-5.30 everyday but I always come home at lunchtime for an hour. This suited our previous dog and she was quite used to being left during this time and was never noisy or distructive. We are going to vist some puppy tomorrow, but my partner is not keen as he thinks it will be left alone too long. We have been offered another dog thats 3 years old and he thinks this would be a better idea.
We cant agree what to do!! Our last dog came to us when she was 9 years old and I would love to experience owning a dog for its entire life – not just part of it. Id like to be able to name it ourselves and have all the joy of training it and building a relationsship with it from birth. We both have lots of time off over Christmas so would be able to settle it in and gradually leave it alone for longer periods so it gets used to it when we go back to work. The other option available to us is a 3yr old dog thats used to having people around all day, it belongs to my partners mum and she said she would happily let us have it….. They are both Westie’s…..What should we do???