I assume you are in PwC. I used to be in PCS tax team and had lots of tax hands on experience not only compliance, provision and audit.
At PCS, you would also be involved in audit support – ASC740. But most of PCS audit is for small private companies. Also, you will get provision prep experience. On the other hand, at ISG, you are assigned in public companies audit engagements and what you are focusing is just audit workpaper write up and Excel tick and tie. To be honest with you. PCS would be a good place to learn more about income tax itself. You have to know how to prepare ASC740 from trial balance not just tick and tie and analyze client date. Once you become a senior at PCS, you could transfer to ISG.
I am now at industry, IT service company tax team. Here, I prepare the provision from FS. Audit is a good skill to analyze tax info but you get to know how to prepare with FS data at industry.
Good thing about ISG is that you will learn how to prepare FIN 18 (interim provision) whereas most of private companies do not follow that FIN18. Also, you would learn FIN 48 as well. I mean, learning lots of preparation at PCS would be better off on your career rather than just starting at ISG…my two cents…