Knowledge-wise both fields have pros and cons since the curriculum followed in our institutions are not updated for BSc/BTech levels. So knowledge-wise comparison is not good here, so I will compare them based on the outcomes of the courses.

BSc Ag. vs BTech Biotech

• Recruitment-wise Ag is better. Agricultural scientist recruitments, state govt etc. UPPSC advertises for BSc Ag passouts throughout the year, though vacancies are low in number. Btech Biotech will bring you no govt job, very less employability in private sector too.
• You can get ok to decent job after BSc Ag, can do MSc to improve your chances and do PhD to become scientists/asst professors in research institutions/colleges/universities. For biotech, BTech/MSc and sometimes MTech will not suffice, a PhD is mostly required.
• Like IT and pharma, Ag R&D has its niche market which is well established isolated and broad. Biotech’s niche market is emerging, negligible Indian R&D and non-isolated market (highly overlaps with pharma, chemical engineering and even IT). So sales opportunity in Ag sector is better. For biotech, sales sector is not developed and mostly goes to pharma field.
• Biotech is ever emerging field, a lot to discover, several opportunities for young minds to be the next great scientist. Though Ag has some good research scope too but surely not as broad and diverse as biotech. But for achieving the greatness time, patience and post-MSc/MTech research is required.

To sum up, if one wants to do research to discover something new then biotech is better but for that BTech/MTech won’t suffice, PhD is the way. For employability, Ag is better. BSc, MSc and PhD in Ag can provide jobs in both public and private sectors.