It honestly depends on the scheme you run in my opinion. Since I will be using a 3-4 in Madden 07, I would want my ILB's to be balanced and my OLB's to excel in pass rushing.
I like a diverse types of LBs on my team. In my Madden franchise I have a fast pass rushing LB, balanced LB (Vilma), and a slower run stopper LB.
I play in a 4-3 so run stuffers are essential to me since I'm always the free safety. I can take away part of the field, as long as they take away the outside run. I have many user picks with Sean Taylor when I play as the Redskins.
Pass rushing. My run defending skill is good enough to stop any running back for a 1 yard gain with any LB... so I'll take the Terrell Suggs like guy to help out my mediocre pass rushing ability. I usually send 6 or 7 guys on a rush per down so pass rushing is also perfect for scheming.