What are the perks and benefits of signing on?

You will have to talk to the recruitment officer for more details. But the perks of signing on is basically as long as you dont make any mistakes, you will be guaranteed a job till you are retired. The pay is very stable as well.

I'm assuming from 'OCS' you refer to signing on as a regular in the Armed Forces.

Firstly, you have to pass the interview and selection before you can sign on. Now that you're in SCS, you're eligbile for the Warrant Officer or the Military Expert Scheme. To cross-over to OCS, you have to be the distinguished honor graduate (gold bayonet holder) and pass their interview. If you decide to sign on after uni, you might uprank faster or start off at a higher level under the ME scheme.

Besides career and financial stability, I think you should also consider whether the job is to your liking. It is harder to transition to other jobs especially if your job scope is rather niche. Unit culture can be vastly different from what you are experiencing now. From the people I know, they signed on mainly as an engineer.