A lifter just starting on their journey into iron really doesn't know the difference between a cheap barbell, a decent barbell, and a great barbell. It's a common joke at the weightlifting gym or box- the beginning lifter grabs the Eleiko barbell, or the really old janky CAP barbell and doesn't know the difference.
Once you've gotten a few reps under your belt, you start to learn. As time goes on you'll know the difference between a great barbell, and a crappy one. If you're in love with lifting, you need to be lifting on a great bar. Your hands will grip better and more secure, the whip as you clean and snatch will help you dial in your form, the smooth rotation of the collars will help you turn the bar on heavy lifts, and your training sessions will be barbell-zen.
Most cheap barbells have a 32mm shaft diameter. Why? Because the thicker the steel, the cheaper/weaker the steel that the manufacturer can get away with.
The problem is that a thicker shaft is not good for a lifter. Great women's bars have a 25mm shaft diameter, while the IWF standard for a men's bar is 28mm. These thinner diameters require better steel, and allow lifters to use a proper hook grip for their lifts.
Even for powerlifting, 28-29mm diameter is specified by the IPF. With the use of both slow and fast lifts in many WODs, 28.5mm in shaft diameter is a great diameter, but that's about as thick as a lifter should go.
There is no benefit for the lifter to have a thicker bar, unless you are training grip strength... and if that's the case, you can do that with special grip tools that will develop your grip strength faster and stronger.
For the slow lifts (bench press, deadlift, squat), a lifter needs a decent spin on the collars, but since the bar is mostly moving in a vertical plane with little rotation, this is not a big deal.
But on the fast lifts (snatch, clean and jerk), the barbell must rotate over 180 degrees, quickly. This means that your collars must smoothly and predictably turn- at the same rate as each other. Great barbells have high-quality bushings or bearings to facilitate this; cheap barbells don't.
One other note on rotation- the bushing/bearing systems used by great barbells age similarly between the two collars of the bar. In other words, both collars will spin about the same when the bar is new, when it is just broken in (1-2 weeks), and even later in life (10-15 years). You won't get the notorious "stuck collars" that cheap barbells are prone to.
Lifters can argue about the "perfect" knurling for days/weeks/months, but it comes down to this: on a great barbell, someone has thought (a lot!) about what that knurling should be. On a cheap barbell, someone who doesn't even lift has stamped out the cheapest possible knurl solution onto the shaft- and probably laid a thick layer of cheap chrome on top.
A barbell must be strong enough to support the weight loaded onto it without bending (permanently) or breaking. Great barbells have a sweet spot where the bar will bend slightly in the midst of a lift, and rebound a bit at the top- this is called "whip". Whip helps you lift more weight and work on your form- but cheap barbells are made of cheap steel, which is very stiff and has no whip.
There was a notorious run of "45 pound" barbells a few years ago for a major big box store that were actually 38 pounds each. I guess those PR celebrations were a bit premature.
One way that manufacturers save money on cheap barbells is to have their quality assurance tolerances set wide- so many cheap barbells might say that their sleeves are at the olympic standard of 50mm. But what they might not say is that their acceptable tolerance is +-2mm off that size.
Our bumper plates inner diameter of the collar is set to 50.4mm, +- 0.05mm, so a barbell sleeve that is even 0.5mm off standard will not fit our bumper plates!
Cheap barbells are mainly made for light use and bodybuilding type workouts. So dropping the bar from even a deadlift height can actually break their sleeves!
A great barbell is made for fast lifts, for Olympic weightlifting, for WODding- and it can withstand being dropped repeatedly.
All great barbells have great finishes. Zinc, chrome, manganese phosphate- these are all finishes that are designed to stand the test of time. And since these barbells are made to last a long time, the finish is designed to age with the bar, getting character as time passes.
Cheap barbells are usually finished with a cheap chrome plating, which is infamous for chipping off as soon as you get the barbell home. Even worse, sometimes the chrome chips off in slivers. Chrome slivers in your hands? No thanks!
You can buy a chrome plated, hex nutted, cruddy barbell for $100-$150. You can buy a great barbell for $250-$1000. At the low end of these scales, you're paying a $150 more for a lifetime of use. This will make sense to most people. And the rest of the world will not get off the couch.
Why do Vaughn Weightlifting Barbells have a lifetime warranty? Because the materials and workmanship that goes into a great barbell means that if it gets to you in one piece, it's going to maintain that basic condition (minus a few cosmetic "character marks") for your lifetime.
A great barbell is one of those "I'll use this for my entire life, and then pass it on to my daughter" investments.
And if you're looking for a great barbell, our Wonder Bar is "very very good", our Bomba bar is great, and the Vaughn Weightlifting Barbell super great! Personally, I lift on the Vaughn Weightlifting barbell.
Any questions? Just ask!