Hi Ian,
Static routes will send ALL traffic for a certain prefix in a certain direction. It doesn’t care what kind of traffic it is…PBR (Policy Based Routing) lets you change the next hop IP address for specific traffic, for example something that matches an access-list.
The “backup” time depends on the timers that you configured for IP SLA.
For your internal networks, OSPF is a good solution because it will automatically deal with failed links and such. IP SLA + Static routes however can be useful for the edge of your network. Imagine you have two ISPs and you want to check if ISP1 is reachable and if not, you can switch to ISP2.
Rene