Back about two decades ago, players started using an extra cue to start breaking with to keep the wear and tear down on their regular shooting cue tip.
Once the trend caught on, the major cue companies came out with designated break cues. The evolution of the break cue went through heavy weights - 22 oz.s up, new harder tips, jump break combinations, etc. until what you see today with phenolic and glass tips.
Robert Bryne back in the early 90's did a study on break cue weights versus breaking speed and found out the fastest break speeds were obtained with a cue in the weight range of 17 5/8 to 18 ozs.
Go to a billiard supply dealer, a cue maker or your friends and try as many as you can before making a choice.
There are a number of posters on AZ who are cuemakers, some of which specialize in break cues.
Don't forget, not only do you want speed but control also.