In terms of CPU performance, the following is a general trend.
Ref:
http://tvboxstop.com/tv-box-stop-2019-tv-box-ranking/
High end in 2019
Nvidia Tegra X1 > Amlogic S922X > Rockchip RK3399
Mid end in 2019
> Amlogic S905X3 > Amlogic S905X2 > Amlogic S912
Low end in 2019
> Allwinner H6
> Rockchip RK3328 = RK3318 = Amlogic S905X
Very low end in 2019
> Amlogic S905W > Rockchip RK3229
I used to recommend Tanix TX3 Max and TX3 Mini S905W 2GB/16GB box for the low end, they are still fine for 1080p streaming but the price may not be that attractive in Lazada/Shopee/Qoo10 or Gearbest.
https://www.gearbest.com/top-brands/brand/Tanix.html
Even the new lower end S905X3 box (2GB/16GB, 100M Ethernet, dual band WiFi, USB 3.0, USB 2.0) boxes become very cheap now.
Tanix TX3 S905X3 official version in Gearbest
https://m.gearbest.com/tv-box/pp_009387038204.html?wid=1433363
2GB/16GB US$34, 2.4G WiFi, no BT
4GB/32GB US$44, dual band WiFi and BT
4GB/64GB US$46, dual band WiFi and BT
It is actually cheaper than the S905X2 based Tanix TX5 Pro (4GB/32GB US$50).
And no point to buy TX3 Max S905W 2GB/16GB at US$40 and TX3 Mini S905W 2GB/16GB at US$26 in this case.
The previous S905X2 based TX5 Max has better feature like gigabit Ethernet and external antenna but the cost is higher. Tanix seems to drop it already.
Of course the above is to compare among generic Android TV boxes running the mobile version of Android OS.
In the sub-S$100 range, Mi Box S should still be considered as the best value box for most of the use cases. Amazon FireTV Stick 4K may be a very good value as well.
On the high end, Nvidia Shield TV (new version in 2019 or the older 2017 version) is still the King. It is above S$200 in general.
In the S$100 to S$200 range, Amazon FireTV Cube 2nd generation may be a good value as well if compared to those Amlogic S922X or Rockchip RK3399 based high end generic box.