@Sean Doherty both are tough areas. I don't own a rental in either area, though I have wholesaled properties in each, because I don't want to own there. Of the two I think Silver Lake might be a smidge better but they're both generally C-/D type areas and you'd be getting C/D tenants.
I don't know that either is really "up and coming" or "going down hill". Upper (and lower) South Providence has had some economic redevelopment type money for specific properties over the past decade, but I don't necessarily feel it's improved the neighborhood as a whole.
South Providence is a closer to downtown, but Silver Lake is closer to the west end which is also nicer so I think they're about the same, if anything Silver Lake is slightly better since downtown/downcity isn't really residential. Plus Silver Lake is near decent-ish areas of Cranston.
They are both tough and you'd be getting tough tenants. But if I had to pick I'd probably choose Silver Lake over Upper South Providence. For Silver Lake, the parts closer to Cranston are better, the parts close to Providence/Olneyville are worse. And for Upper South Providence the more north or east you go the better, but it's all tough.
If you are serious about either/both areas then next time don't just drive through, get out and walk around, maybe talk to some older people who live in the neighborhood, maybe go look at some apartments or open houses in the areas and talk to the showing agents. Especially the apartments, that will be your competition if you buy there so that's a double win.
@Anthony Thompson I had a suspicion that they're tougher areas. I came across a couple properties that I thought were worth a little more of a deep dive but I didn't get much info from the clerk I talked to at the Police Department so I figured I'd reach out to the BP community instead of just relying on Trulia's crime maps. Thank you for your detailed response.
I actively own properties in both areas. Silver Lake over the last 20 years has transitioned from a predominately Italian neighborhood to predominately Hispanic. I have maintained excellent tenants in this neighborhood and have no complaints.
South Prov is a bit different. There are little pockets that have been revitalized, but as a whole it is not an ideal area. This city is very funny. There are little subsections within neighborhoods. Unless you know those pockets, it is difficult to generalize an entire neighborhood.