Definitely the 620 if you want to stay on the cheap side. The only thing I'd be worried about is the smaller screen, so if your dad won't mind that then it's the way to go!
No love for Huawei? Ouch! Their Androids are decent, and I expect the same for their WP8 phones. That coupled with the fact that the W1 will be the cheapest WP8 and middling specs leads to my (and possibly only) recommendation for the W1.