At that price, definitely not, I'd only consider it if it was the other way round.
27" 1080p is barely enough to hide the pixel lines, which probably make you want to sit back a little further to make them less apparent. This manuveur also defeats the entire purpose of a larger monitor.
Yeah it's an interesting topic, without going into arc minutes I see a lot of people buying a 4k monitor only to not benefit from it at all, in terms of resolution. Here's a great chart which tells you if you benefit from your purchase, mind you I already got your point, higher resolution sure helps but you can't see the pixels, if you can the monitor is damaged.
a 970 will shine at 1080p without a doubt, there will very few instances where your card will be worked up.
at 1440p however a single 970 would struggle somewhat, even 980 alone can't reliably drive the resolution without sacrificing some details, but for most older games, 970 or 980 should manage pretty well.
4k however is in a completely different league. Currently no hardware on this planet can drive the resolution reliably, even 2x Titan X's have problems.
That means someone that owns those two monitors reply, which is not the case here, but experience enough to judge price to performance when it comes to monitors. Since the second one is only 3" larger, and 200 more expensive, the obvious answer is that the contrast and color is worlds better on the second monitor. No doubt.
When it comes to monitors, or TV's too for that matter, you can't just ask that question, because numbers never tell you enough, size & resolution are the only things we know for sure is correct, everything else is there to make you buy their product because bigger numbers = better in most consumers eyes. Most brands measure things such as contrast and color differently, so without looking at the two monitors side by side, it's impossible to tell.