I've said it before and I'll say it again, stop spit-balling about what shape teams' salary caps are in. Nobody knows, you can't work it out from hearsay about player contracts.
I don't think there's any doubt Hawthorn would be offering more than Sydney. Mitchell would be Hawthorn's second best on-baller (behind Mitchell), he's Sydney's 4th/5th best.
But being second best will come with a lot of responsibility. He could be the type of player that loves the responsibility or he might decide he'd rather be the smaller fish in a more successful team.
Money will be a factor but so will many other things. I still wouldn't be surprised if he went for Carlton on much bigger coin than Hawthorn or Sydney are offering.
If I was a Hawthorn supporter, I wouldn't want Mitchell to be too money hungry, because he'll get more at places other than Hawthorn. Which is why I think it will be difficult for them to land him.