I think the main difference is that in the D.R. you can largely do as the locals do - eat chicken from the street, shop at the colmado, take the guagua, go to a public beach etc etc...
In Haiti living like a local is not something most blans would want to do.
OK, so I eat the street food, buy fruit on the street and take the odd moto, but when it comes to housing I would not live in a corrugated iron shack in a ravine with no electricity, water or security.
Tap-taps are just too damned hot and inconvenient - and in some cases risky - and the beach, if you live in Port auPrince, in just not on at all.
You need to head south and west for an hour and pay to enter a drab private beach club for a few dollars or head north for an hour and pay US$25 to enter one of the soulless beach resorts there.
In the D.R. you can do these things, in Haiti, mostly not.
Maybe if you are a tourist wanting to experience the 'real' Haiti it is OK for a couple of weeks, but to live full time like an average Haitian would have most people running for the airport after a few days.
Therein lies one of Haiti's problems - living conditions suck for most Haitians.