For the most part, a motherboard is a motherboard. They differ in feature set, but performance varies by a negligible amount in most cases. Some may OC better, or work better at high RAM speeds, or have a slight power efficiency advantage. But if a given model has the specs you need, it's probably good as any other.

As far as differences between the Sabertooth and Pro, they're pretty comparable. The PRO has an Intel USB 3.1 controller, vs. the ASMedia on the Sabertooth. Sabertooth only supports up to DDR4-2400 according to ASUS's spec page, which is weird. I've never seen that on a Z170 board. The Sabertooth also has a bunch of "TUF"-branded features that I cant say much about, and an apparent 8+4 phase VRM and 5-year warranty against the PRO's 8-phase (or possibly 8+2) and 3 years. I'm not enough of a MB guru to know how important the VRM stuff is. Sabertooth has two SATA Express, PRO has one (6 SATA total on each). PRO has one more PCIeX1 slot.

For similarities, both have: 1xM.2, x8/x8 PCIe support, Intel 219V LAN, Realtek 1150 audio, and USB 3.1 Type C, along with all the other stuff that's standard on most, if not all, Z170 boards.

If you wanted to go for a Pro, you probably just need a Z170 A. The PRO GAMING also has red accents- so if you don't want red you shouldn't get it. The Z170 A is pretty great.