First off, there aren’t many quality DAPs at this entry-level price range that I know of. The antiquated Cowon i9, with no Wifi and no storage, or the Sony NW-A25... For both, sound quality is decent, though nothing to write home about (I had both). Other than that it’s Chinese devices, from brands various degrees of established. The Fiio X1, then offerings by Cayin, Hidisz, Lotoo... that push towards 150$+. None of them, from what I know, are spectacular.
The only big rival as far as DAPs go is the Shanling M0, with a similar form factor, a great DAC/amp (the same as in the LG V30), LDAC and aptX support (though no aptX HD), an SD card slot and a small screen. It’s a great alternative if you don’t want to depend on a BT source, and you can work with a UI made in China - still a no-go as far as I’m concerned.
The ES100 shoots above its price in terms of SQ too, only around the 300$ mark will you start to see it beaten slightly by DAPs I’d estimate (Fiio X5, Pioneer XDP-30R...).
I got the ES100 and favor it over the M0 for the same reasons I replaced my DAP with a hi-fi phone. It’s a more modern, versatile device. It relies on the latest Android UI. It supports high-res streaming, not only with Wifi but also with mobile data. And you get both LDAC and aptX HD.
The ES100 is for the times when even a thin, light phone is still too cumbersome. It is controlled by an amazing, clean-looking, powerful app. It even does balanced output. And the updates add whole new, significant features - more sweeping changes than the bug fixes and belated translation improvements that make up the main fare of Chinese manufacturers’ updates.