Premium Service Central membership gives you priority notifications, so as a job is posted it's immediately sent to you via SMS or email. Service Central will push the jobs out to you, and you can choose which ones you want to accept. Tier 3 pricing is used on the referrals (between $7.50 and $30).
Jobs Board membership* gives you access to the jobs online through your Provider Portal. Service Central will wait for you to find the jobs yourself and accept the ones you want. Tier 2 pricing is used on the referrals (between $8.50 and $35).
*The Jobs Board membership has been replaced by other options effective 1 August 2010.