Benoit wasn't really the 4th member of his 4 horseman group. It was Flair, Benoit, Mylenko, Then 4th of there group of Mongo and Pillman. Arn was manager. So it isn't really safe to call Benoit a 4th member.
In my opinion it was Ole because he was the original. However Windham was the man and very underutilized in his career.
Before I get started, I must correct the following. In the first incarnation of the Horsemen to include benoit, he WAS the 4th 4th member, as Pillman was the third. Pillman eventually slipped out of favor and slide to 4th, but Benoit was originally the 4th.
Now, to answer the question of who the better 4th member of the Horsemen was out of the three choices, I will answer by the process of elimination.
Ole Anderson- I don't give a shit if it was called the Minnesota Wrecking Crew or not, Ole was a pussy. He didn't have the stamina to stay and he was a mainstay in an irrelevant faction of the Horsemen. When he came back, he just didn't seem to have that same toughness or drive and was a moot player if anything. I was glad when Tully teamed with Arn to replace Ole. It made for a better, grittier duo. So no, not Ole.
Barry Windham- I'm sorry, alot of you look at his size, his credential, and his lineage, but Windham was a fucking hack. He was "Dusty Rhodes-lite" during his whole NWA career and never came out from Dusty's shadow, in my opinion. I mean what the fuck does it say about you when you need a prop called "black beauty" to get over as a heel? It says you aren't that believable on your own and that you more than likely only wear assless chaps because you are gay. He just never fit the Horseman mold if you ask me. So nope. not Barry either.
So who does that leave? Oh god, don't make me have to tell you. Fine, I guess.
It's........
Lex F'N" Luger bitches! I mean when the Horsemen were the top heels and ran roughshot over the rest of the NWA, they were about "limousine riding, jet flying, wheelin dealin, and kiss stealin". Neither Ole nor Barry fit this mold. Only one man pulled off the mantra by just standing there in his rob, letting his million dollar muscles speak volumes without him having to say a word. I mean every fuckin time I saw Luger standing there with the Horsemen, I got a fuckin hardon because that was what the Horsemen were supposed to look like. You have Flair as the crown jewel, Anderson and Blanchard as the rough cut stones on the flank, Lex Luger as the perfectly chiseled diamond in the rough, with JJ Dillion holding it all in his hands like a million dollar mogul.
I dare any of you to go back and star at interviews of the Horsemen. Not the individual ones, but the ones where the whole groups were there. Go ahead and watch your Ole Anderson ones where the group seemed blue collar and weren't really that hated. Then look at the ones with Barry Windham, were he didn't even seem to fit in with the look of the group and people only hated him because it was like Dusty Rhodes Jr. going heel.
And then humble yourself and take a look at the interviews with Luger standing there. Feel the hate creep from within your stomach. And then ask yourself this, why does this faction bring forth this feeling? It's because they were those millionaire boys who were down and dirty and did WHAT they wanted WHEN they wanted. The got the money, the cars, the girls, and all the titles. And Luger only helped further this look as the blue chip member. Shit, the closest they got the recreating this was when Paul Roma was the young cocky member. But it wasn't the same. And it only went to show you that they were trying to recreate the most successful and potent Horseman look. Plain and simple.