My 2 year old has a huge set of Mega Bloks that he loves. I bought them for him when he was a year old, and I chose Mega Bloks because they are larger than Duplo, so I thought they would be easier for him to build with. Now that he has mastered the Mega Bloks, my husband wants to buy him Duplos. I'm wondering if it's worth the investment, since they are only slightly smaller than Mega Bloks. Should we buy him Duplos and then later on Legos, or let him use the Mega Bloks until he's ready for the Legos?