With the Bronstein, you can see what time you exactly have, whereas with the Delay, you can't (clock freezes for the time free).
What do you prefer between Bronstein and Delay ?

I'm probably just confused here, but don't most people just refer to it as an increment? And yes, prefer it to delay.
So you both think that Bronstein is best.
In fact, I wondered why the Delay is prefered to the Bronstein in the USA ?

Yep, now I'm officially confused here (an all too common occurence ). I thought Bronstein was delay mode, and I thought increments were called Fisher.
Increments are called Fischer, while Delay and Bronstein are, well, delays : it means that at each move you have a "free" time to think before your time starts to go down. The only difference is that Bronstein "adds" this free time (free time is set at the beginning on the clock), so you can actually see it on the clock. On the contrary, Delay "freezes" the time on your clock during your free thinking time, it means that your time will remain the same during the free time and will start to go down only when the free time is used.
What do you prefer between Bronstein and Delay (way of displaying time on a chess clock) ?
See the following video if you don't know the difference between Bronstein and Delay :
http://www.youtube.com/watch?v=Hpj7wLY6olA