should I use circular needles or doubble pointed??
which one is easier…
help is greatly appreciated.
The method that is easier is the method that is easier for you.
Only you can answer your question.
what kind of hat are you knitting?
there are lots of hat styles!
but --really many hats can be knit flat and seamed, or in the round.
and many patterns can be converted to flat (from round) or to round (from flat)
Flat knit hats have 2 extra stitches. (these will get ‘lost’ in the seam)
flat knit hats (vs round knit hats) need alternate rows of purls if the pattern is basically a stocking knit
(and round knit hats (from flat patterns?–2 few stitches (no seam and no 2 stitches need for seam allowance)
and round knit hats are worked in all knits (for stocking knit)
Nicky Epstein almost always knits her hats flat… she doesn’t have too many free patterns out there… but lots of books have her patterns --look (search on ravelry to find images/sources) for her patterns if you want a flat knit and seamed pattern.
For knitting hats in the round (which I prefer cause there’s no seam to sew!), 16 inch circulars are usually what are called for. To me it’s easier because you just knit around and around verses having to switch needles like DPNs. It’s all in preference. If you use the 16 inch actually you’ll need DPNs for when the number of stitches with the crown decrease gets too small to fit on the circulars.
You can also do hats with magic loop, which wouldn’t require you to switch to DPNs later.
You can try different methods and find the one that works for you 
What does DPN’s stand for???
Double pointed needles, the short ones like socks are knitted on, but they come in larger sizes too which can be used for mitts and hats.