I'm just new to quilting, but I found a box of 200 for $8 that were size 2 nickel plated straight safety pins. My experience with them was that they went through all the layers easily and I closed them up using a soup spoon to lift the points. Really easy!
I think the curved ones are to make it easy to close without moving your quilt, but the spoon helps close them easily and I've had no problem with the quilt moving.
I saw on the really expensive "quilters" pins that it said they were safe to leave in the quilt for extended periods, but from what I could see they were just straight nickel plated size 2's so I went for the large box - 200 was the same price as 45 pins and identical product.