Machida has quite a history of smashing boxer/wrestlers, and that's a weight class up.
He's smart enough to know he can't be as tentative as he was vs Rampage in the first two rounds of that fight. He learned his lesson there.
Styles make fights, and Machida is SOOOOOOOOOOOOOOOOOOO much worse a matchup for Weidman than Vitor would have been or even than Silva was. Here's why:
Weidman is a grappling phenom. Anyone who disagrees should look up his grappling match vs Andre Galvao. He have Galvao all he wanted, and Weidman had been training bjj for less than a year. He's a BJ Penn type prodigy in what his learning curve was, and that's not something I'd say lightly. Plus he had the wrestling pedigree to start with, which Penn didn't.
Weidman also has the ability to do serious damage once he takes guys down, even in their guard. Silva found that out in the first fight, which is why he started trying to goad Weidman into standing and not taking him down. Silva found out very quickly that it was much different getting hit by Weidman while on his back than it was vs Chael or Travis Lutter.
So why all the Weidman flattery if I think Machida is such amazing value? Because Machida has something that neither Silva nor Vitor have: a track record of stellar tdd (and again, that was against bigger guys a weight class up). Guys like Silva and Vitor have to consciously think about being put on their back at all times against someone like Weidman. He's a better grappler than they are, and can smash people once he takes them down. That affects the striking game, and is a good example of why one skill blends into another in MMA. Weidman's striking feeds off his grappling, and vice versa. GSP had the same abilites, keeping guys constantly off balance.
But Machida doesn't have to worry as much about that as those other guys. He (rightfully) will have far more confidence in his ability to keep the fight standing. And while I believe Weidman has more power, Machida is the more well rounded and more dynamic striker overall. He has the advantage in a fight that stays standing. Maybe not a big advantage, and Weidman could certainly catch him and finish him, but the odds of this fight are simply off. It happens, and good bettors take advantage.
For the record, with no $ involved I'd absolutely be rooting for Weidman in this fight.