Nectar collectors are much more portable than an oil rig in that they are smaller and designed to be held and moved around. The main function of nectar collectors is that they can be dragged over concentrates to be inhaled.
According to SmokeCartel, “A nectar collector is a new trendy way to smoke concentrates instead of a dab rig or oil rig. These tools are unique among smoking gear in that they vaporize but they are not vaporizers. They are portable, but they’re not hand pipes. They can use water, but are not water pipes or bubblers.”