When we moved from Upper Manhattan 4.5 years ago, we narrowed it down to Riverdale vs Jackson Heights. There absolutely are very nice apartments quite cheap in Riverdale. I would not assume they are in bad parts of the neighborhood. But--the 1 train is far away from the nicest apartments, which are next to the Hudson River. People take a bus down to the 1 train. There are also express busses and Metro North--which you have to take a bus to even from close by, unless you want to walk down a long, steep staircase or down a long, winding road to get to the station. And trains don't run often except at rush hour. Thus--transportation is definitely more difficult and you really have to have a car in Riverdale. There is much more natural beauty, river views, parks, etc, than in Jackson Heights. But much less nightlife--fewer restaurants, cafes, and retail in general. It's more suburban. Plus many of the apartments are located close to the main roadway, often overlooking it, with associated traffic noise. All in all, we chose JH for its much better transportation options and much livelier street life and artsier, less conservative vibe. Also it's true that the maintenance fees are higher in Riverdale, but you do get parking, doorman, etc for those fees. So if you want a nice, big apartment with a terrace, river views, gym, sometimes even an outdoor swimming pool, parking, doorman—you can get great deals in Riverdale without a doubt. I think it's the remoteness and the large amount of postwar hi-rises that keep prices on the low side up there.
