Trying to decide on a motherboard for my first ever pc build. Also, from where I'm buying, the tomahawk costs about 10~20$ more than the Strix.
Depends on the ports/connections and features that you need/want.
Specs-for-specs, the Asus ROG Strix B350-F Gaming is the better motherboard than the MSI B350 Tomahawk:
Asus has 8 power phases | MSI has 6 power phases Asus has 6 SATA ports (all 90-degree oriented) | MSI has 4 SATA ports (only 2 in 90-deg.) Asus has 3 PCIe x16 slots (2x v3.0 in x16 or x8/x4 + 1x v2.0 in x4) | MSI has 2x PCIe x16 (1x v3.0 in x16 + 1x v2.0 in x4) Asus has 3 PCIe2.0 x1 slots | MSI has 2 PCIe2.0 x1 slots Asus uses Intel I211AT LAN controller | MSI uses Realtek RTL8111H LAN controller Asus uses ROG Supreme FX S1220A audio codec | MSI uses Realtek ALC892 audio codec Asus has a total of 8 USB ports at the rear panel | MSI has a total of 6 USB ports at the rear panel Asus has 2 USB3.1 Gen2 ports | MSI has no USB3.1 Gen2 ports Asus has 1 USB3.1 (19-pin) internal header | MSI has 2 USB3.1 (19-pin) internal headers Asus has 2 RGB LED Strip headers | MSI has 1 RGB LED Strip header Asus has RGB Ambient LED Lighting | MSI has Red-only Color Ambient LED Lighting