Great question: different tools for different jobs. The Ohio Deadlift Bar is specifically for just that - it’s slightly smaller diameter makes it easier to hookgrip and hang onto in general, as well as letting you start from a stronger position to lift slightly more weight. Many powerlifting federations & strongman shows I compete in feature them, so this lets me practice how I play.
The thick one is an Axle Bar. It’s 2” diameter and would be the antithesis of the deadlift bar - the axle has zero whip, no collars or bearings to rotate (this makes cleans much harder), & challenges the grip heavily. It is common in strongman shows for both the clean & press event as well as the deadlift, and can serve as a great tool to build grip by doing timed holds with it or using it for accessories like curls. They are cheap and durable.
Lastly, the silver one is a cheap chrome all-purpose bar. I use it for pressing, squatting, most of my barbell work. This is the important one; if you only have one barbell it needs to be what you want to use for everything. Something like a Power Bar if you want center knurling for heavier squats, or a weightlifting bar with a smooth center section if doing more cleans/snatches or CrossFit training.
There are others out there like the Squat Safety Bar that allow you to keep your elbows much lower on squats to unload the shoulder joint and train your upper back more, Swiss/Football Bar for neutral grip pressing, the Squat Bar which is extra thick and long to support heavier squat weights without the bar oscillating the way a Powerbar will above 400, the Log which is the most common pressing implement in Strongman, and so on.
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