For get a better choice both are good but diploma is not a graduate degree so when you go for finding job you can only apply for 12th pass jobs or diploma applicable jobs rather if you do b.sc in agriculture you got your granulation degree as well as you are applicable for all granulated, diploma and 10th, 12th oriented jobs.

For finding best college in b.sc in agriculture you can visit here

https://university.careers360.com/colleges/list-of-bsc-in-agricultural-science-degree-colleges-in-india

For finding best diploma college in agriculture you can see here

https://engineering.careers360.com/colleges/list-of-diploma-in-agricultural-engineering-colleges-in-india

Thank you. I hope this answer helps you.