I wouldn't mind seeing Siver fight Guillard again, just so he can be sent back down the ladder again.
I have nothing against Siver as a person, but the fact that some people rate him above Guillard is funny. In 2008, Guillard finished him in under a minute. Since then, they both have only lost once. Siver lost to Ross Pearson not too long ago, and his only good win is a close decision against Sotiropoulos, a guy who is probably a good match up for him. His only other two wins after his loss to Pearson are against Winner, a guy who I'm not even sure if is still employed in the UFC, and against an out of prime Spencer Fisher who is probably going to be retiring soon.
Guillard on the other hand, beat a solid fighter in Gleison Tibau right after and has only lost to Nate Diaz since his win over Siver. I'm a fan of Diaz, but it's safe to say that Guillard had the upper hand up until he got caught in that guillotine choke. Melvin has gotten smarter since then. He is on a 4 fight winning streak, and has picked up wins over a game Jeremy Stephens, and Evan Dunham, a guy who was supposedly a bad match up for him and had a lot of momentum going into their fight. Guillard didn't beat him by a close decision, he finished him in the first round decisively.
Needless to say, but I think that Guillard is ahead of Siver in the rankings and I'd like to see him prove why he is again.
It is all about matchups outside of the elites at 155(Gray, Frankie, and BJ if he goes back) really strong guys who Soti can't completely tool standing are going to have a good chance of beating him, very good wrestlers and fast strikers have a good chance at beating Siver, guys with a combination of either good wrestling and bjj or good wrestling and powerful striking have a good chance of beating Cowboy. You can go down the line for basically all of the guys in or near contention and find a few peers who are just awful matchups for them.
Which makes who is ahead right now not matter much since they are going to have to win likely 3 more fights to even get a title shot. Whoever gets the most favorable matchups will get a shot one of them is losing before then though probably both if they are getting matched against other top 15 guys. Guillard should beat Roller easily. I think Wiman is a better fighter than Roller and has a good chance of upsetting Siver. If Guillard has to fight Bendo, Miller, Pettis, or Guida those are very losable fights for him. The fact that Bendo and Miller are fighting eachother in what is probably a number one contender fight helps Guillard more than Siver not having the greatest strength of victory. Both of those guys probably beat Guillard 90% of the time.