Diego, KenFlo ,Maynard, Stevenson, Guida > Edgar
Ok so pretty simple right and now...
Penn > Diego, Kenflo, Stevenson, Guida, Maynard and last on the list Edgar..
look at it this way...
How long would you give Edgar in a fight Vs GSP ??
Frankie hasnt faced anyone...he beat Sherk....WOW!!! The none juiced up Sherk at that....A sherk that wanted to show off his hands and sucked!!!
Frankie may seem like a nice kid but I would dish out 50$ to see him Vs Guida before seeing him out classed by Penn!!
Edgar should go to WEC and try and get a title run up there, cause it aint happening here.
Styles make fights. GSP would maul Edgar because he has godlike takedowns and is heavier, and Frankie' BJJ isn't good enough to nullify St. Pierre's on the ground.
Whereas, BJ Penn is a BJJ prodigy with mediocre takedowns, great TDD and great boxing. Frankie Edgar's base is wrestling and he has shown dramatically improved hands over his last fights. BJ can pretty much ONLY hope to outbox him, and vice versa with Edgar.
If Sanchez could last almost the whole fight with his subpar technique, then Frankie has a chance getting deep into the fight, and possibly getting a decision.
If you look at the lightweights you listed, none of them really match up well against BJ. Stevenson's strengths are the same as BJ's but worse, Kenny is small, susceptible to takedowns and submissions, and his striking isn't enough, Maynard/Guida/Sanchez rely on wrestling and pace and wouldn't be able to take BJ down at his current conditioning, while BJ has them all killed in the standup.
Edgar has shown great boxing in his last couple of fights, arguably better than any other lightweight challenger. Does it mean he can beat BJ? No, but it makes him as good a choice, or better, than any other fighter in the division.