A break cue will not make you break any better. This is all PURE HYPE generated by the billiard industry, and cuemakers. I love all the theories behind compression of the tip, and the cue weight. You are all starting to sound like Bob Meucci. Lighter isn't necessarily better. Neither is a harder tip.
An effective break pockets balls, and leaves the cueball in a specific spot to shoot from. There is no cue out there that promises to make 4 balls on the break. Notice no cuemaker makes any speed promises of their cues? You are hitting a round, hard ball with a wooden stick that compresses when you hit the ball. If the tip doesn't buckle (in the case of a phenolic tip), the shaft will. People think that by stiffening the shaft and putting a rock hard tip on a cue, that it adds speed. It does, but at the price of accuracy. If you hit the cueball 5% faster, but hit the head ball 10% less squarely, you are getting negative return with the higher speed. Same with a lighter cue. It's easier to swing a light cue faster, but you will hit the ball less accurately. How much accuracy are you willing to lose to gain a miniscule amount of speed? Look at the chart from Platinum Billiards when they speed tested the break cues. There is not a lot of variance between leather tipped cues and phenolics. If you watch break shots in slow motion, the cueball is bouncing on the way to the rack. The cue ball seems to bounce around less at slower speeds. The rack seems to spread better too.
It's like the guy that goes out and buys the latest driver because he wants to drive the ball 300 yards. If he can't hit the centre of the fairway with most of his drives, it was a bad investment. Same with a break cue. If you're destroying your tips on your playing cue, or breaking shafts due to your 30+ mph break shots, then go get a break cue. If you're an endorsed pro, carry one because it doesn't cost you anything. What I laugh about is there is a 2/3 rank on our team that carries a break cue with her. I don't. I pound the rack with my playing cue (20.75 oz). I've never had a tip problem (actually helps to break in the tip faster) or shaft problem, and I know EXACTLY how my playing cue hits because I use it for every shot.
My 2 cents.