An Olympic bar has revolving sleeves which makes any exercise smoother. These bar's are also match bars which means, in theory, better balance, ease of handling and all of the same standard weight, give or take a few ounces. Though not all Olympic bars (and plates) are made the same. Cheaper bars from India and China are usually poor quality and mixed weight (those special sells of 300lbs BB sets for $99.00 for example). But China can make higher quality Olympic bars, though more profit on the cheaper stuff.
An exercise bar is one pieced roll bar, giving a stiffer and more ridged performance. Their inner sleeves ( if equipped) are fixed. Like lifting dead weight, while an good Olympic bar feels alive and with a slight spring to it. Nothing wrong with an exercise bar for working out with, most people do. But you can add 10 to 20 lbs more to a exercise (depending on the exercise) with an Olympic bar.
All in all I would suggest an Olympic bar for BB curls. Just because of the smoother and better balanced bar. Feel like you are not fighting dead weight so much with a better flow to an exercise. Even an Olympic style EZ bar over a exercise EZ bar.
If wanting a different slant of BB curls (Olympic or exercise bar) grab in the center of the bar and do one arm curls standing. May take a little getting use to the balance, but calls into play a lot of supporting biceps and forearm muscles that are not usually hit by regular curls. Good Luck.
