That's a tough question for any of us to answer. My first reaction would be to say that you should do what you're the most comfortable with. But, if that is sidearm, then I have two cautions for you. First, a lot of coaches aren't comfortable or knowledgeable in dealing with sidearm throwers so that could forever be a battle. You may get a lot of bad instruction.
Second, you really need to make sure you don't open up the shoulders too early. You need to adjust your timing so that your shoulders are squared up at release. If you struggle with this, many coaches will tell things like "slow down", "stay back", "don't rush", etc. But what you really need to do is get the hips going and get into foot strike quicker. If you have a habit of opening up too early, you put more stress on the arm than is necessary. Over time, that wear and tear can add up and lead to injury.