Which has better career opportunities: SAP ABAP or BASIS?

Both comes under technical area however there is HUGE demand for people who know both ABAP and BASIS. Vanilla installation and system maintenance of BASIS people is not much in demand but Architects are paid a lot. If you have expertise in ECC, EP, CRM, HANA etc.

BASIS is more demanding field than ABAP and salary wise BASIS offers much better compensation. BASIS people often work on weekends, with downtime etc. This is in general not with ABAP people.

Both comes under technical area however there is HUGE demand for people who know both ABAP and BASIS. Vanilla installation and system maintenance of BASIS people is not much in demand but Architects are paid a lot. If you have expertise in ECC, EP, CRM, HANA etc in BASIS then demand and package will be much better. Same goes for ABAP, if you know JAVA, WebUI, UI5 etc ABAP HANA then you will be bettter positioned.

Personally I would have avoided working in BASIS sole reason that often you have to work in off hours, long hours and on weekends.