What's your opinion: onion seeds v onion sets?

Your opinions on the question of onion seeds or onion sets would be appreciated. 

 I have never planted onions and would like to do so this year but even after weighing the pros and cons I can't decide.  Seeds=more product @ less cost;  Sets = less product @ a bit more cost, but saves time.  Ideally I would like to harvest up to 100 onions storing and dehydrating.

Thanks for your help.
Keep warm  :)