Best Route selection due to ping times

I have an internal corporate network of 20 sites and have mikrotik on all of them. Every site have 2 Wan connection (1 for hotspot users and the other for voip and internal stuff). Sometimes one of the connection perform poorly with high ping times (of about 300ms to 500ms) affecting VOIP and other services. I just one to know how can I acomplish best route selection due to high ping times between my sites. The connection doesnt quite timeout.

Alexps2