Pros of USMLE
1-The best part about USMLE is that you get to do what you want to do. Its not like Indian PG in which to get IM, you need to rank 800 maximum, otherwise if rank goes down, you might have to do something whichyou don't like.
2-You get trained from the best healthcare systems of the world. As it is well known, the USA healthcare system is the best and you get exposure to variety of things, whatever you read in the book, as the protocol, you get to do that. Like for Myocardial infarction, we know the protocol says that we should do PCI within 90 minutes, but there are very few hospitals in India which have Cath Lab facility.
3- Opportunities for research, almost all of the hospitals and universities in the USA, have research opportunities available for the residents as well as doctors. You get to be updated with the changes occurring in the healthcare, and contribute yourself.
Cons of USMLE:
1- Time taking process, USMLE consist of three steps along with need of US clinical experience(Electives, observerships, externships), if you start early during medical school, it can be done. Yet, if you start after medical school, it takes almost two years of effort.
2-Expensive process: Money plays a big role in USMLE, each and every step along with Qbanks, travel, and stay in the USA is expensive. You need to have backup or earn this money by doing job and study for USMLE.
PLAB takes less time and money to prepare. Self learning for a long time for exam preparation will not count on CV. You do not want to have a long career gap. After passing PLAB, you can apply to any specialty ... most candidates apply general medicine but there are plenty of jobs in Trauma and orthopaedics, Emergency Medicine, General surgery, Psychiatry, Paediatrics ... You are also allowed to work 20 hours/week, so if you completed PLAB and you can work as a locum. After being in UK, you will be more seasoned with language and culture.