For me, the AP200 has too high an output impedance (NOTE: I've since learned that the OI on this is actually higher than on the AP200), and runs an older version of Android than this one - a big drawback. The R6 is also running a Snapdragon 425 SoC vs the RK3188 in the AP200.
The Rockchip SoC will cost less, but will be a slower chip. That rockchip is a quad A9 core processor. and it's actually a pretty odd choice for a DAP given that it's designed for tablet use (big batteries) or Smart TV dongles (plugged in to the wall), and wasn't even marketed for use in smaller mobile devices. It's possible it's actually the RK3188T, which is underclocked, has a bit slower GPU, and is therefore lighter on battery use.
The Snapdragon is, I think, a 20nm quad core, and quite a bit faster. Still, we're not talking world-beating performance here, it's going to be a 2 year old entry level Snapdragon. But a 2 year old entry Snapdragon is going to outperform that 4.5 year old "High-end" Rockchip. High end as per their marketing, of course, but pretty decent performance in its day.
You're not going to find a Snapdragon 845 and Android Oreo in a DAP. Your only shot at something even close that would be if Sony had to dump extra chips they bought for their phones and decide to make a ZX3, and that's not happening. I think a 425 and Android 6 is pretty good for a first run at an Android DAP. I was considering the AP200 as well, but I've opted to skip that and will probably go for one of these.