First thing, it depends on the size of your hands. If you have a big hands, maybe u need to use a bigger barrel or a chunky one and if you have a smaller hands than you need to use a small or slimmer barrel.
Second thing, are your hands dry or are there moist. If your hands are dry than any kind of barrels will suit you because just the slightest bit of grip, you will be fine. Where as, if your hands are moist and they tend to sweat a lot than you going to need a barrel with a lot of grip because when you are under pressure and your hands are moist, the darts will slip unless there is a lot of grip on it.
Personally, i am using a straight and a full grip barrel as shown above. There are many, many shape of barrel to choose from but it comes down to personal preference that you decide while trying different darts or barrel. Your preference may change over years of playing darts. As you proceed in your darting life,do not afraid to try new types or style of darts. Through out the years of playing darts, i have changed , nearly 30 to 40 sets of barrel. It takes a lot of experiment before you can finally find the PERFECT barrel for yourself.
I hope my post is useful for any newbie out there, who is maybe thinking of getting a dart barrel for themselves. "Jangan marah ya..Share2 saja."