In short, JLPT2 demonstrates that you have a basic functional understanding of Japanese for business. This is the certification you need if your main task at your job is doing something that doesn't really require Japanese ability (programming, writing English, etc.).

The JLPT1 demonstrates that you have significant language skills, enough to reliably read Japanese at a near-native level. This is the gateway certification that you will need if you want a job that uses Japanese, or if you want to enroll in many programs at Japanese universities.

Cheers,
Kaeru