...technically any free game you download via PS+ is not yours, you cant keep, nor sell, nor trade it... only play it...
Semantics. Technically any paid game you download via xbla
is yours, but good luck trying to sell or trade it.
My hypothesis was you could buy the console and pay the subs and not need to buy any games - so we'll take the payment of subscription fees as a given in that scenario. Own it or rent it makes no difference in practical terms on a digital download, so long as you keep paying your subs. It's just a name. The reality of it is that once you've paid your subs you can download any game they offer you at no extra cost, and you can play that game as much as you want - that month, years later, whenever you want. Just like owning it.
Now I'll confess I know little about PS+, but my understanding is you usually get around 3 games a month for ps3 and a couple for vita. I'll ignore the vita element of that (though the inclusion of free games for that handheld plus it's integration into all ps4 games makes it a compelling purchase) and I'll assume that releases for the ps4 will be similar to on the ps3 - so around 3 games a month. Assuming of those 3, one is a good game you haven't played before, one is a mediocre game you haven't played before, and one is a game you've already played (sound about right? I have no idea, but that sounds fairly likely to me) that means every month you're getting a good game, a mediocre one, and occasionally a game you've already played before - for around £3.
That's enough to tide me over nicely. I probably average around one good game and one mediocre game a month on the 360, but I pay for them. I usually wait until prices drop, but it still adds up to quite a lot of money. And I pay my gold subscription. I could sell those games, but I usually don't - I like to have a catalogue available to me, even though I don't often go back to games I've completed. And if I did sell them I wouldn't get anywhere near the difference in price between buying them on xbox and getting them for free on playstation.
(Another consideration, but this is entirely personal preference, is I quite like digital copies of games rather than physical ones - partly because there's no disk spinning, so it's quieter and less likely to fail, but mainly because I have a bad back and my console's only a few inches from the floor - so I hate changing disks!)
I don't want to sound like I'm hailing the ps4 as the saviour of the generation. There's a lot of stuff I don't like about it, and there's a lot of stuff about the xb1 that I really do like. I'm just putting forward the argument that ps+ seems fantastic value to me.
As for your argument about pc gaming being the better option in terms of keeping annual costs down, I'm in complete agreement - as you know, I'm seriously considering having a steambox or other pc hooked up to my tv instead of a console next generation.
NB I couldn't be arsed to put quote marks around all references to "free" games, but if we assume you're going with the subscription service on whichever console you buy (which I would do) then to all intents and purposes those games are free.
