I spent nearly 6 months looking at homes in almost all parts of Oakland before finally buying a triplex in the millsmont area. Oakland is very block-by-block. One street could pass for any other suburban area (not even a city!) and the very next could scare the **** out of you. Look at the numbers in every opportunity without being emotional about it and don't forget to account for maintenance and unexpected expenses. Many houses also have a lot of deferred maintenance, so expect to sink a few thousand dollars to fix the deferred issues upfront. No point in fixing them later on when they blow up into emergencies..
Which opportunity works for you depends on your goals and strategy. E.g. A house may have a long time rent controlled tenant and that will drag its price down for investors.. But as an owner occupier, it may make complete sense for you. Then again, its a once every few years thing, you cant do it more frequently than that.
If a property has market rents, it will command a better price.. but then again, if the rents fall (and they have fallen in the past couple of years), you may be left paying a very large mortgage.
For me, the best bet was to buy a stable property with long time tenants with not too low rents, that was also cash flow positive. If such a property materializes, the lower than market (but not ridiculously so!) rents offer you a margin of safety.. Even if the market rents go down, you are still cash flow positive because you can still raise rents at 2.x% that the rent control board will allow you to.
All said and done, Oakland will continue to 'gentrify' and the number of people projected to live in this area is probably an order of magnitude more than the number of new houses being built. So in the longer run, the neighborhoods and the quality of tenant should keep getting better.
Just remember to not over pay, run the numbers and maintain a margin of safety in your investment and you should be fine.