If you only commute at <30mph and have a standard exhaust you probably don't need earplugs however if you ride any faster or have a noisy exhaust then I'd definitely recommend them.
I've tried dozens of types and tend to use the foam ones when I'm doing a long journey as they drown out the most noise but I use the rubber ones for shorter trips as they're quicker to insert and remove as well as allowing a bit more noise through.
I've tried dozens of types and tend to use the foam ones when I'm doing a long journey as they drown out the most noise but I use the rubber ones for shorter trips as they're quicker to insert and remove as well as allowing a bit more noise through.