What MTG Fat Pack Should I Buy?

I recently started playing Magic The Gathering. So far I bought an intro deck, a Mirrordin Beseiged fat pack (which got me a Tezzeret, which I then sold to my local card shop for 6 Beseiged booster packs and 5 scars of mirrordin booster packs), and a few extra Beseiged packs here and there. I want to buy another fat pack, but I'm not sure which to buy. I feel like buying another Beseiged pack would be redundant, since most of my cards are from that expansion. I'm tempted to buy a Core 2011 Fat Pack or a Scars of Mirrordin Fat Pack. Any suggestion on what to buy next?