To answer the question... i believe the draft has proven out that Corner is the position that takes priority.
Just look at the top 10 over the past few years, or the first round as a whole...
Going back the last 3 years... Rolando McClain, Sean Witherspoon, Aaron Curry & Brian Cushing are the only LB's taken in the first round by a 4-3 team. McClain is debatable, Oakland switches up so much it's hard to say what he plays.
There have been 10 DB's (Counting Malcom Jenkins as a corner) over that same 3 year span taken in the 1st round.
So the simple answer is Corner is the premium position over LB in a 4-3 defense.
Is that because of positional importance or because the DBs have been better prospects than the LBs the last few years?