I don't know about SLI 970s at 1440p, the VRAM is already a serious problem with one. Adding another one will represent a limited value.
I'm using it to downsample it from extremely high resolution with very, very high settings.
GTA V for example works great!
A 970 alone is a very good 1440p card, two are 2880x1620 cards.
I normally downsample and set 2xMSAA and almost everything to max and it works great for 50-60fps.
Please stop making it worse than it is, a 970 is a smart choice if you're not made out of money and want the price/performance ratio card from nvidia.
And two of them are at least as performing as a 980ti.
There are of course some games (like Trials Fusion or Fifa 15) which don't work with SLI but those games are not that demanding.
Especially with X12 in the horizon (which fixes almost any SLI issues and vram is now doubled!) 970s are a REALLY great choice for gaming.