They're probably both natural 155'ers, but Eddie started his career as a welterweight, he's not the smaller man. Not as tall, but Alvarez is stocky and strong for 155. He's also incredibly experienced. He's beaten some of the toughest guys in the world. He's beaten Shinya Aoki, he's had wars with the incredibly talented Michael Chandler, he beat Kawajiri when he was still a monster, and he's won 3 straight in the UFC. I do think Conor will beat him, he's only really looked good in one of his UFC fights but Alvarez is a top lightweight that has beaten some of the worlds best, has a huge gas tank and can wrestle his arse off. Conor's got a tough fight on his hands here.
I think the rest of the card is fantastic. Can't wait for Woodley vs Wonderboy, I love watching Joanna Jędrzejczyk, Weidman vs Romero is a battle between two top middleweight contenders in a stacked division, Cerrone has looked phenomenal at welterweight and faces a tough fight against Gastelum, Tate-Pennington is bound to be fireworks, Edgar-Stephens will be a war, Khabib returns, Rashad returns, Thiago Alves makes his 155 debut and takes on Jim Miller in what will likely be a crazy war. This card is absolutely stacked top to bottom. Easily the best card the UFC have ever put on.