For many devices recently on the market, the streamer is integrated with a DAC and possibly preamp capabilities (volume control, source selection, or both). So chances are, you won't be hearing the "streamer itself" in isolation from one or more of those other functions. Furthermore, streamer A and streamer B may be delivering different combinations of software effects (DSP) or source content, which all color the output. FWIW, Stereophile does not have a separate category for "streamers" in its annual list of recommended components. They have a "digital processors" category, which mostly covers DACs (many of which have integrated streaming or preamp capabilities, equalization, DSP, etc.)
So, while In theory "everything is important", I doubt that anyone here has done controlled, volume-leveled A-B comparisons among multiple streamers in a way that focuses solely on the streaming functions, per se, of all the compared devices. I'd venture to say that the impact on SQ of the streaming capability, per se, probably is somewhere between negligible and unobservable compared to the impact of the DAC and especially the preamp effects. But I don't really know for sure, and would welcome anyone to point out a good comparison of multiple streamers, one based on some credible combination of metrics and expert observation.