There was about 2 pages of discourse on Harbor and other So Cal programs starting on page 4 of the thread, they will probably answer most of your questions.
In summary, I chose Harbor because I felt I would fit in there the best. I thought the residents were the most confident and brightest I have met as a whole, they come from top med schools and most go on to excellent fellowships. I feel it is the best place for clinical training in So Cal and will give me the best chance of going on to a competitive fellowship, and I like the fact that they take their own residents. With that said, the program is certainly not for everyone. Residents seem to be given more autonomy and responsibility than most places and if you come from an institution where you are used to asking your attending if you can write for prn tylenol, you may be in for a shock. The program is all county and I am sure that if I ended up there I would probably do a blood draw or two, and maybe even have to transport a patient, but I am ok with that. To me, Harbor seemed like a very "old school" place in that regard, and I guess I like that.
I think the patient population, the faculty, and the housestaff are the biggest strengths of the program.
As far as UCSD, I thought it was a good program, just couldn't get all that excited about it. I am sure I would be happy there, but to be honest, I don't know that much about it.
Read that previous thread, if you have more questions, let me know.