Oil Bongs and dab rigs are both great smoking devices that use percolation to filter vapor or smoke. Between the two are some differences, like how you use them, their size and even the price can differ.
The main difference between dab rigs and bongs is what you will consume out of them. Dab rigs are designed to smoke concentrates, like oil and wax.
Bongs are made to smoke dry products like herbs, weed and tobacco.