Overall, the Z97 and H97 chipsets are really only incremental updates. They add PCI-E M.2 support, but otherwise the chipset itself is exactly the same as Z87 or H87. One of the biggest benefits is really in that it gives motherboard manufacturers like Asus a chance to make improvements on their existing products. The chipset might not be much different, but the new Z97 and H97 motherboards overall have much more balanced feature sets compared to their predecessors.
If you are considering upgrading from Z87 or H87 to these newer chipsets, we would advise against it in most situations. You simply will not gain much in terms of features, and nothing in terms of performance. If you are in the market for a new system, however, there is really no reason to not use a Z97 or H97 chipset instead of the previous generation.
