I suppose at first glance, without seeing a minute of either one play, you could make comparisons between Miller and Maybin. But Miller was a much, much better player than Maybin in college, and it's not even close.
Miller understood football coming into the NFL, and his tackling and run pursuit are getting better by the week. He's simply far smarter and far stronger than Maybin, despite the similar weight.
There are many all-pro and pro bowl OLBs playing around 240-250 lbs (see Harrison, James). Miller is only the latest one.
It was a bad comparison back then, pre-draft, and it's a downright ridiculous one today.