Traditional IRA vs. 457(b) - is one preferable?

I am a state government employee, part of a state pension plan as my primary retirement saving.

To supplement that, I have been contributing $100/month (post-tax) into a traditional IRA through Vanguard. Through my employer though, I also have the ability to contribute to a 457(b), and I am just wondering if it would be more advantageous to me to roll my IRA over into the 457(b) and begin contributing to that instead? I guess I am just confused over the pre- and post-tax contributions/disbursement differences between the two, and wondering if one plan is more beneficial to me than the other.

Thanks in advance, and happy to provide any additional info!