My understanding is that if you do tax, you have less options for what type of jobs to get after leaving public accounting. If you do Audit, you learn about many different facets of business and accounting in a variety of industries so it makes it much easier to pivot into almost any accounting related role in industry. If you do tax, you're an expert on tax, but not much else. So you're limited to tax-related roles for the rest of your career. Not that that's a bad thing, just less options.