I don't think there's a definitive or logical answer, it mostly depends on various factors; I'll try to list the ones that come to my mind:
the argument: if it's something difficult I think it's better to state your opinion at the beginning; for example, a theorem is always explained (at least in my books) following the order hypothesis > thesis > demonstration, otherwise the student might get lost because he doesn't know the destination of the logical path;
the quantity of arguments: especially if you're talking, if you start your speech from the arguments the other might want to respond to each of your argument, and you might lose the thread;
your style: if you expose your thesis in terse statements, then I think you can start from the arguments; if you're like me and love to write/say long and complicated sentences (especially with a refined style), then you should state your thesis first, so that the other knows what are you getting at (this is also the reason why this post is taking me so long);
your task: is it to persuade someone? Then start from the thesis. Is it to prove you know something thoroughly (at school,...)? Then build your speech from the basis, but be ready to state the answer if you get stuck while exposing your line of reasoning;
your istinct: it's up to the other to listen politely and ask if they didn't get something. Speak however you prefer.
Notice how I just used "method 1" (which is my favourite when writing); if you read this wall of text, I did a good job I also wanted to use the "bulleted list"