Pros
Looks great on your resume and down the line if you continue to pursue accounting in public or private. The experience you get here will always be valuable no matter where you go. The training you get is excellent, though that really depends on which engagements you get placed on. I had a particularly tough client and huge team so was able to learn loads. Every skill I had from my previous mid-size firm was honed to a higher standard at EY. There are further opportunities outside of audit if that's not your thing. But if you want to get in to Forensic. FAAS, or TAS, it's doable but very difficult. Bring it up with your counselor/partner to get placed on M&A audits if TAS interests you. Make sure to build on skills that interest you so you can leverage them down the line; try dabbling with Alteryx/Tableau if data analytics interests you.
Cons
Appearances are valued too highly. I came from a mid-size before joining EY and went right in to busy season with one of the most notorious clients in the NY office. There was a large learning curve and the client made things worse. After busy season, was placed on Performance Improvement Plan, was told it was nothing to worry about by counselor and HR. Later on was able to roll off to a different client completely and realized how much easier it was and got a better review. Then was called in by HR and a partner both whom I never met before and was laid off. It's terrible how the people who get to decide whether you stay or leave is determined by someone who has never worked with you (in this case one of my counseling partners). Also, plenty of people get bad ratings but are still at EY; these people simply get shifted off from one engagement to another engagement to deal with. It's important to ensure your counselor and team truly have your back when things get tough so they can vouch for you. Also, my general advice is, if you're placed on PIP, start looking for another firm as it's hard to salvage.