I have the same answer as anyone else: Mozilla FireFox provides a lot of SEO tools. so you can check the pagerank, the do-follow attribute and much more. But Chrome is doing a good job also, with more and more SEO plugins.
Since Browsers are not concern of SEO so the question is not correct. But now comes the GOAL of SEO i.e. conversion at last. So if your site is cross browser compatible it will display the same on all the different browsers, so before starting your SEO you should check it for compatibility. validator.w3.org is one of the best place to know about the potential problems about the compatibility.
If you are concerned about the tools available to the different browsers for help in doing SEO, every browser has a tool similar to one available on other browser.
Yeah, FF has a lot of add-ons that tell which links are nofollowed, and that type of thing. However, I reallly do think that a lot of the SEO tools aren't NEARLY as valuable today as they were a few years ago.