Geekbench 3 results for the new MacBook Air and MacBook Pro models have arrived on the Geekbench Browser. I've generated some charts that compare the new Broadwell-powered laptops with their Haswell- and Ivy Bridge-powered predecessors.
Keep in mind that Broadwell is a "Tick" in Intel's "Tick Tock" model. Generally speaking "Tick" processors improve efficiency while "Tock" processors improve performance. As a result I do not expect the MacBook Air and MacBook Pro scores to increase significantly.
Single-core performance has increased 6% from Haswell to Broadwell, and multi-core performance for the i5 model has increased 7%. However, quite surprisingly, multi-core performance for the i7 model has increased an impressive 14%.
If you're thinking of buying the new MacBook Air I would strongly recommend the i7 processor. It has 20% faster single-core performance and 25% faster multi-core performance for only a 15% increase in price.
Single-core performance has increased between 3% to 7% from Haswell to Broadwell, depending on the model. Multi-core performance has increased 3% to 6%. These sorts of increases are in line with what I would expect from a "Tick" processor.
I have no recommendations regarding the processor for the new MacBook Pro. The performance differences and the price differences between the processors are roughly equivalent.