I am working on a kind-of-racing game in unity with what I would call quite high-end graphics.
You can achieve quite a good look, at least on PC, with good performance, if you optimize, optimize, optimize... and then optimize some more.
While UE4 might give you more headroom (don't know really, never used it and haven't seen a real benchmarking comparison), you will find that even with UE4 the situation changes little. No free lunch there too.
So I personally would advise you to stick to Unity as you seem to already know the engine, if you can spend something.
Why only if you are able to spend anything? Getting really high-end graphics with Unity cost me about 1600-2000$ in money... you will need the Pro version for the Image Effects, soft shadows and deferred (And the profiler for easy optimazations), and some Black Magic from the Asset Store to improve the weaknesses of Unitys out of the box shaders and systems. Like a good Terrain shading system, some helpers for creating race tracks, dynamic weather systems and stuff like that. If you want to go really nextgen, there are multiple good physically based shader systems in the Asset Store (one of them, Lux, is even free!).
If you are not able to spend much, you will loose out on a lot of stuff in Unity. Nothing a crafty programmer could not get around with some code (there are image effect systems that don't need Unity Pro, so you could write your own SSAO System I guess, same with soft shadows, or the bumped / parallax terrain shaders)... but of course that needs a lot of time and skill to pull off.
If you can spend only 20$, UE4 sounds like the best solution for you. That is what the total engine package with no upgrades after a month will cost you.
Of course, with my 2000$ I got some Systems for generating Race Tracks and stuff like that that you will miss in UE4. But of course, again, nothing a crafty programmer couldn't write himself.
And I get free upgrades for the full Unity 4 cycle, which translates to 2 years or about 240$ worth of UE4 subscription time. But again, I guess you can just pay another 20$ if you see something interesting coming up in a new release after a year or so without paying all the time, so yes, at the moment UE4 IS cheaper than Unity PRO.
Be aware though: Thanks to UE4 the playing field changed dramatically for Unity, that is most probably why Unity 6 was announced so suddenly (I expected it at least 6 months later) and why a lot of things became free (hard shadows for Unity Free version, Android and iOS Indie is now free)....
Who knows, maybe the cost structure will be changed again when Unity 6 comes around, maybe more stuff will be available to Unity free users (hopefully replaced by even more functions in the PRO version).
Time will tell... but something to keep in mind.
Edited by Gian-Reto, 12 August 2014 - 07:16 AM.