The 690 is a very .. very old card already .. and I didn't buy it for crypto mining but rendering.
My point is that it sux that my old card has after so much time till more cuda cores than any new you can buy.
And the Titan Z.. well ..who in the right mind will buy that one!? I wonder if they every sell one such card for the price they dream. So forget about that one.
The 690 was in the price range of a normal card back then.
What sucks, is that a lot of people are still buy into the obvious marketing moves and don't really take the time to learn the differences in fine print. You are comparing two very distinct architectures on a single metric, and one that does not even translate directly into any absolute benchmark reference point. Manufacturers take advantage of this to squeeze every last bit of profit that they can with each product generation...
Let me put this in other words: How performing/fast are the individual units of cuda cores for each card? What's their relative memory bandwidth? What are the base & boost clocks? What's the overclocking headroom? How tolerant is the cooling design towards sustained usage at max TDP? Are there any hardware instructions exclusive to either architecture? What are their respective compute levels? What are their relative efficiencies?
I could go on and on, and these are just the most basic specifications, most of which are certain to be listed on any product page (once a product actually exists).
I for one, am very interested in the 800/900 series, as these will be super at dual duties. A pair/trio of these in SLI will be a massive game setup, and even if we're stuck with 28nm, the Maxwell generation is well proven to be efficient at mining. The 750TI might even continue to be the most cost effective choice for mining (or perhaps the most efficient in pure W/hash), but it is really just for the casual, low-res gamer as it is entry level and has no SLI support.
For mining alone, density should be an important factor, but only for those that might call themselves "farmers". I have a single game PC/rig, and a spare PC that I can assign to mining duties if I need to move some 750TI's around. So personally, I don't care for density all that much (yet?).
~ Myagui