Since OP is dealing with a chihuahua, he should probably stick with Puppy Linux indefinitely. The chihuahua lapdog series is really great for lightweight fun and portability, but comes at the cost of storage space, and so larger distros sometimes cause problems. This is most often the case with the classic "small dog syndrome," the distro thinks it's in a larger dog than it actually is. You can also often get memory issues and shake.exe launching repeatedly due to overstimulation errors. Puppy is so small it typically avoids these.
Alternatively, if you ever want to upgrade to a larger model, I'd recommend Black Lab Linux. It's more robust, powerful, and really easy to train to your needs. Plus, it's retriever times are amazing.