It’s actually a personal choice. If you are actually interested in both, then go for the college. The better one you choose. Pulmonary is an excellent choice in which one can superspecialize further in fields of paediatrics, emergency etc. But the scopes remain restricted to pulmonary.

Medicine offers you the versatility to go to any field after 3 years in which you are interested including pulmonary superspecializations. 

Even you may practice as a general physician which is a diar need of the country.