I would honestly stay with Verizon if I were you. My sister has one of the cheaper android phones on straight talk and recently had her plan completely cancelled because she went over 2gb of data. She called their customer service line and spoke to a representative and they told her she broke their terms of agreement and she asked , "how when you advertise unlimited data?" And they actually hung up on her. She was 16 days into the month of service I believe and had to go buy another card. If I went with straight talk there's no way I would pay for the full year at once.
Not worth it in my opinion. Either way if you're trying to get "unlimited data" on straight talk or verizon you're going to have to pay for the full price of the phone, so if I were you I would stick with Verizon.
Now my mom has had no issues on straight talk, but she barely uses any data.