The quick answer to this question is that one places more emphasis on the hamstring which basically takes away from the total weight that one can lift in the movement. The other movement, on the other hand, works the entire body with eve distribution of the weight.
Conventional deadlift is for those who:
- Would like to lift more weight in general mainly because of the even distribution of weight
The romanian deadlift is for those who:
- Would like to improve flexibility in the hamstrings and glutes (which is why you mainly see people performing this movement when they’re trying to work their hamstrings)