I myself don't have a total grasp on all of them and their variations, but they are different molecules with different receptor/transporter affinities, which makes up the differences in their effects.
Example being that Fluvoxamine is the most selective of all the SSRI's, it goes for only the SERT with negligible NET or DAT affinity. For some reason it's also known as being one prone to adverse effects (violent outbursts in particular).
Paxil has notoriously been known to be the 'strongest', most effective SSRI, but with all the side effects that go with it, namely a high risk of suicide when starting on it and horrific withdrawal when coming off of it.
I was on venlafaxine (effexor) years ago, but after a week at the lowest dose I stopped because it made me so stimulated. Like a really psychotomimetic amphetamine. I would get wired and watch the X-files all night; at first it was fun, but it wore me down. I dropped it and never went back to reuptake inhibitors, especially because at that point in time I was tripping about every 2 weeks and didn't want to impede my adventures. After that I knew I never wanted to permanently be on a substance with a phenethylamine backbone (venlafaxine, bupropion being the main ones).
Looking at it now (with how little I trip), being on an SSRI with little NET affinity is actually quite good in me. Citalopram seemed to be a good choice for being a straight SSRI with good effectiveness, and few side effects. Doc pushed the on-patent single (S-) enantiomer; escitalopram. Being on insurance I figured what the hell, could only be more selective with less stuff for my body to process.
As to your initial question on comparative efficacy/side effects; yeah they're all different but it's much too complex an issue to be summed up in a table. You do have to go reading; affinities and adverse effect frequencies give a basic understanding of which has a tendency for what.
I thought mirtazapine was going to be my panacea from anxiety (that was not a benzo), but man, what an antihistamine effect. Imagine taking 10 benadryl; that was it. Mirtazapine knocks you out flat and makes you helplessly delirious all through the next day, until you take another pill to get knocked out again. I was FUBAR. Tricyclines and tetracyclines are for severe cases; their affinities for so many receptors (non-selectivity) makes the side effects unbearable.
SNRI's or DARI's like bupropion are better for depression in people who aren't edgy to start with. I'm a skin and bones wire-case; always have been. Anything that enhances stimulation or inhibits apetite is no bueno for me, but good for many others.
So far SSRI's to me are something you don't feel; it's just in the background.