You may be trying to decide between a bar with a center knurl like this, this, or this and a bar with no center knurl like this, this, or this.
There is not a definite right or wrong answer. Any of these bars will perform well at just about any task you throw at them, but different bars are optimized to really excel in certain areas. It all depends on what your predominant use will be for the bar. You need to ask yourself some questions as for whether or not a bar has a center knurl is only a small part of picking the right bar for you.
Will the bar be used predominately for powerlifting movements, Olympic lifting movements or both?
Will the bar be used in CrossFit workouts?
Here is some discussion to help the answers to those questions to help guide you to the perfect bar to fit your needs.
If you will be predominantly Powerlifting and only occasionally Olympic lifting a good power bar will serve you well. The center knurl will help keep the bar in place on your back during back squats and on your chest for front squats. If you are not doing cleans and thrusters you will not have to worry about scraping up your chest. Even if you are using a bar with center knurling for traditional Olympic lifting workouts a center knurl may not bother you, because the number of repetitions is not typically that high. In fact, all certified men’s Olympic lifting bars have a center knurl. However, if you are doing Olympic lifts during CrossFit workouts you may end up scraping you chest raw.
If you will have separate bars for Olympic and power lifts or of you almost exclusively Olympic lift, you will love the dedicated Olympic lifting bars or even the hybrid bars without a center knurl since you won’t end up with a permanent abrasion on your collar bones.
If you are competing or considering competing in Olympic weightlifting or Powerlifting, not only are you likely to lift more with a dedicated bar for that sport, you will also be lifting with an implement that is a close as possible to what you will be using in competition, helping to eliminate at least one variable on competition day.
Dedicated Olympic bars have bearings or bushings that ensure that the collars will spin freely 100% of the time which greatly reduces the likelihood of a wrist injury. Since many of the athletes that Rogue caters to, do a variety of lifts, most of the bars we sell spin well enough to keep you safe when Olympic lifting. However, a really fast bearing bar, may not be the best choice for bench press, since the spin may cause the weight to feel wobbly, making the lift more difficult and less safe.
If you will be using the bar for CrossFit workouts and both Olympic lifting and Powerlifting, a good hybrid bar like the Rogue Bar or the Burgener Rippetoe Bar may serve you well. They will stand up to abuse and do well in all the movements.
There are many other variables and many other questions you can ask to find the perfect bar for your situation. Read the descriptions carefully and don’t hesitate to ask questions to ensure that you get the best product available for your situation.