I have both the rook 4 and the New Apple tv. Got the Apple TV over black friday for my basement TV, and got the roku 4 yesterday, to go with a new 4k TV.
The Apple tv has the better interface, in terms of being pretty to use. The roku's interface is more functional and efficient. The my feed feature, and search ability is great. Siri is smarter, but the universal search of Roku searches all the services available (minus iTunes, of course). It eliminates the need to check multiple apps to see if a movie/show is free/cheaper on different services. The roku has every streaming service one could want (again, minus iTunes), and that is a big plus, making it the better cord-cuter device. Both perform really well.
Apple TV: Pretty and smooth interface, better for gaming (I haven't tested this, I game on current gen consoles), has iTunes. Airplay
Roku: More functional, efficient interface. Content agnostic, more (all) services. 4k. Cheaper price for equal performance.
4k is huge, and a damn shame apple didn't include it, when the hardware is more than capable. If you don't have a 4k, it might not matter to you, but you can't say it doesn't matter to the industry. Go to, for example, Best Buy and try and buy a TV (like I did a few days ago). 4k TVs are everywhere, and affordable. A good example is the Vizio E class (1080p) vs M class (4k) The E class is a damn good, affordable TV, with a great picture. The M class (based on the sales on amazon and best buy) is only 100 or so more for, example, the 50 inch ($499 vs $629). The M class is rated as one of the best looking TVs you can buy right now. Put them next to each other, even with 1080p content (due to the technology in the 4k panel) and the M series looks significantly better. Then, when you play 4k content, it blows you away. Its not just the resolution, it is the color and contrast.
Once you use 4k, you see the difference. I love my 60 inch plasma, which my Apple tv runs, and will keep it for as long as I can...but I have to admit 4k looks wondrous on my 50 inch Vizio. 4k is the new thing, and will really take off this year....just as 4k content is really starting to build up.
If the Apple TV streamed 4k, I probably would have go another Apple TV. But it doesn't, and so I got a roku 4....and I really like it. It is cheaper, and its approach to content is superior. For a streaming device that cost $150-200 (roku is $120) its ridiculous. The Apple TV offers less content (streaming, not games) and capabilities then the roku. I love my Apple products, and really enjoy Apple as a company. But it seems this is a blatant approach to withhold a feature for the 5th gen Apple TV. Why else would they limit the 4th gen Apple TV? If the current Apple TV had 4k, why would one need to upgrade anytime soon, minus gaming power? We can hope for a software update, but why gimp the Apple TV out the door. It only hurts sales, as in my case.