It looks like Firefox is every-so-slightly less bulky than Chrome. However, that square tab is an eyesore. It calls attention to itself in both its garish design and its bright white hue matched against a more subtle gray backdrop.
I want a taskbar to do all but disappear when I'm browsing the internet. I can't believe I'm saying this but, visually, Microsoft Edge is the best one.
F11
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Once you're aware of your own art, you can train yourself to identify and replicate the "good" ones... And hands off the bad ones.