Without knowing your computer; The Radeon card is more powerful but runs hotter than the GTX 780 You're taking a big jump between cards so make sure your power supply and cooling system are up to date.
To make decisions like this, I usually just go here. PassMark gives the following scores (card, bench, bench/price): (GTX 780, 8044, 16.12) (R9 290, 6320, 14.70) Now, I am not sure if the benchmark score is truly linear or not, if it is, the GTX 780 appears not only to be the better performing card but also the better value.
My GTX 580 has been doing just fine for me the last two years, along with my Core i7-2600K. I don't really see the need for people to fiddle with their stock settings.
New games come out and with them higher system requirements. If you're fine with lowering the settings keeping the same system for a few years works out fine but if you want 60+ fps on max settings with newer games you need better hardware. For example, I upgraded my monitor and now need a better graphics card to run my games at my preferred settings.
i have the r9 270 oc card, works great but i put in a 750 watt power supply strapped 2 cards together works like a champ