Personally, I love Addi needles--they're very slick metal.
Some people will have the same passion for bamboo--because they're NOT slick.
You can knit back and forth on circs as well as knit in the round, so you can get away with only have circs if you want. I find I still use straights on small things because it just seems easier--plus I knitted for years on only straights, so they're comfortable. On anything medium to large, though, I find myself reaching for the circs--they are a bit easier to knit with and the weight of the item gets distributed evenly. You also can't lose one in the couch cushions! :rollseyes: