Personally I'd say Dilmah is the best that NZ has to offer! And i'm probably the most obsessive tea drinker on the planet!!!
I've got some yorkshire tea in my cupboard, brought with me on the plane almost a year ago now, and once my taste buds switched to Dilmah (and yes there is a kind of taste bud adaptation thing you need to go through) i can't stand the taste of Yorkshire tea now....it has some weird aftertaste that Dilmah doesn't.
For tea fanatics out there planning to try Dilmah based on my advice, make sure you avoid the Dilmah afternoon tea, it tastes like gnats pee. Try regular Dilmah, or English breakfast. There is a Dilmah extra strong, but i've never tried it and think the regular stuff is good.
As for Choysa and Bell - don't bother. You need 2 tea bags in a cup to even get a remote taste of anything (and it still doesn't taste like tea!)
As for the taste bud thing - when I arrived here i thought weetbix tasted like dry cardboard - of nothing basically - now i think it's scrummy!!!!!