Well from what I there is a localised effect from IM injections AAS as well as systemic, which is most likely to be greatest with short estered gear.
As for sub Q cycles, I havent done it with EQ yet but thats another obvious choice. The main benefits for me are simply the ease of doing it and being able to give your injection sites a rest, and being able to inject 2x per day for more stable blood levels, which with tren is a big plus. Its not a problem with long estered gear injecting twice a week but for me at least short estered gear is a pain. I'm also interested if there's going to be any localised fatloss effect.
It also opens up a new way of getting started for those who are needle phobic. Plus in the event of an infection, the consequences are likely to be much less serious, and the probability of infection from SQ injects is minimal. Anyone whose unlucky enough to have had an abcess would probably be pleased at the idea of SQ injects.