Having used both, I'd take a proper trendline over linear regression any day of the week for the my purposes at least.
Elliot Waves and other wave count generators don't work - at least I've personally never seen it hold up with any consistency over time. But they do make convincing charts after the fact as the historical wave counts and locations change with the current market price action. Again, that's been my own observation.
LR IS objectively produced whereas trendlines are not, that's the point at hand , it's irrelevant what you think.
Nothing really 'works' but again that is not the point. EW are hand drawn rubbish, they could improve no end if you knew what you were doing. But hey it's up to anyone what so called indicators they use