Welcome @Reut Eitan
It really depends what you're looking for. Are you going to occupy this property for a period of time before renting? Are you looking for an up and coming neighborhood for appreciation, or are you strictly looking for cash flow? Do you want to be near the bars/day-night life, or would you rather be in a quiet neighborhood? Baltimore can offer it all, it just depends on what your strategy is.
Canton happens to be my favorite neighborhood due to its close proximity to 95, major shopping outlets, the water, and overall positive vibe of the Community. Canton will ALWAYS rent. I repeat, CANTON, WILL, ALWAYS RENT. At times, I have seen people pay more for a bedroom than they should just because "inventory" is low. However, parking is an nightmare and its harder to get a deal and or good entry price point.
Highlandtown has a lot of movement right now. If you're closer to the Patterson Park side you can get more in rental prices. Honestly, some parts of Highlandtown can't even be differentiated from "Patterson Park". Crime is still a huge problem as you get close to Orleans st. I personally wouldn't touch anything on the "400" block from Rose to Highland (just my opinion though).
I lived in Federal Hill when I first moved to Baltimore. "Fed" is more of a younger crowd (at least in my experience), but it was nice to be close to Camden Yards (and the Harbor). I feel like the houses are a bit smaller than Canton but the rental prices are still up to par with the nicest neighborhoods in Baltimore. Crime is really low.
This is all South Baltimore, there are a ton of great neighborhoods to live in Northern Baltimore as well. It really just depends on what you're looking for.
-Eric