My background: I have cleared all three steps of the USMLE with my Step 1 and 2 scores in the 250s range given last year and have subsequently cleared NEET PG 2018 with an AIR of 565 (99.56 percentile). I have chosen to pursue MD Radiodiagnosis in India after my results.
Although both the exams are significantly different in terms of their approach and question pattern, there is a fair bit of overlap given that the subjects remain the same. Please bear in mind that the USMLE prep will be helpful for NEET but vice versa is not true. USMLEs are entirely clinical based with no rote learning whatsoever. NEET PG too is moving towards that direction although it isn’t completely there yet. My USMLE prep cleared my basics especially in subjects like Pathology, Medicine, Biochem, Biostats, ECGs and image based questions which are asked very often in NEET PG in the recent years. The USMLE exams last for 7 to 8 hours in front of a computer screen with questions that are often two pages long with 5–7 answer choices and many distracting lab values, thus the 3.5 hours of NEET with mostly one liners and four options seemed like a cake walk and I was very comfortable with the computer based exam pattern.
Most people asking this question are not sure of which exam they wish to focus on. I do not recommend preparing for both exams and parallely and trying your luck in whichever you happen to crack. Both exams need utmost dedication and focus with the USMLEs needing you to plan your schedule and finances for the next 2–3 years given the requirement to travel to the US for Step 2 CS, clinical electives, interviews etc. Don’t plan on keeping your feet in both boats. Both exams are similar in terms of difficulty and that should not be a criteria while making a decision at all. Decide where you want to live and work and plan to excel the necessary exam accordingly without spending any time on the other one. So ideally, such a situation where USMLE will help you in NEET will only arise in rare cases like mine where I was planning to go to the US and settle down, but after clearing all my steps I decided to drop the US option as I had a change of heart and decided to settle down in India itself.