If you are talking exclusively about delivery systems. Bitrate.
At it's peak Netflix accounted for ~35%+ of traffic on the Internet (around 2014-2015 era) alone. Times have obviously changed since then. Not because it had more users than YouTube or more playtime but because it was delivering long-form content in high resolution. Which at the time was a considerable technical challenge, from bandwidth and distribution itself but also to encoding infrastructure.
More broadly Netflix also had a profound impact on the CDN landscape. They made use of all existing CDNs (Akamai, Cloudfront, old stuff I forget) while also building out their own POPs, they paved the way for modern CDNs in many ways. The style of which would eventually be cloned by many players but most importantly Fastly. Fastly would then go on to provide this service to new players like Bytedance to rapidly deploy massive delivery capability with very little ramp-up.
They did some less-cool things ofc, they bowed to the HDCP mob and did dumb things like build a Silverlight based client etc.
By and large however Netflix has had a positive impact on the industry.
YouTube on the other hand (after acquisition) was largely built with Google tech on Google infra.
The only major project to come out of it isn't delivery related is Vitess - a sharding system for MySQL.
Its largest impacts on the industry are unfortunately much less savory. Mostly pioneering inventions like pre-roll ads and targeting based on content in which the video is embedded, heinous recommendation algorithms that send people into procrastination spirals etc.
Well that isn't entirely fair, we can thank Youtube for pushing for better encoding standards and tangentially through Chrome making HTML5 video not suck (arguably though, Safari/Webkit was also influential there).