You can differentiate the two by looking at which is closer to pre-illness behaviour. I've been on citalopram for ten years now, and my mental state and personality on the drugs feels very similar to how it was before I became ill, apart from a few of the usual side effects mentioned by other posters. My initial reluctance to go to the doctor was absolutely a consequence of the disease. In addition to being depressed, lethargic, and anxious, I was worried that the drugs wouldn't work (and that I'd therefore be stuck without
any future hope) and simultaneously that they
would work and I would end up a different person.
As for dose and med, I was fortunate in that I responded to the first SSRI prescribed (citalopram). Fiddling with the dose is trivial, though. Once you're on top of your condition the doctor will probably take your lead if you suggest going up or down, and in any case your own customised dose is merely a pill cutter away even without your doctor's permission.
[Standard disclaimer that SSRIs are unlikely to solve the underlying problem, but can buy mental scope to address it, etc. etc. They can also be difficult to withdraw from (I'm now on my third go) so it's not like they're a panacea, or in way "happy pills"]