Size & shape of the needles really does matter.
For example, on the oversized charcoal scarf I'm using huge size 15 bamboo needles. And my hands are killing me by row 4. So I've been doing 4 rows at a time, so I get one pattern iteration each time.
With my hats, the size 4 16" circular Boye needle is okay. I think the needle is plastic, which is a bit odd, as the cable seems heavier than the points. But with working in such a small round seems to make my hands work differently, and I can only do a few rounds before my hands hurt in a different way. I got the Silverlume size 3, 16" and the needle is much longer and more comfortable, but the bends in the cable at the end of each needle bend so much I'm afraid they are going to break. It's much better than with the previous needles.
I also have a ribbed scarf on size 6 straight needles. But the ones I were using were so long it was excessive, and none of the local stores sell short size 6 needles - so I got a set of clover dpns and put point protectors on the ends, and it works wonderfully.