US vs City

What are the advantages of training with a US firm? Will I be guaranteed a seat in New York if I go the US route or are they just sweat shops?

I’m planning to apply for training contracts over the summer and can’t decide between US firms such as Weil Gotshal & Manges and Cleary Gottlieb and City firms. What are the advantages of training with a US firm? Will I be guaranteed a seat in New York if I go the US route or are they just sweat shops?