Hi Madison511! It is a matter of personal preference. I personally feel both bars have their advantages depending on what exercise you are doing and what you are looking for within each workout. For instance, the EZ Curl bar, though shorter and bulkier, works great for varied hand grips and wrist comfort on many exercises such as lying tricep extensions, bicep curls, overhead tricep press, deadlifts, bent rows, reverse curls, etc. The straight bar can also perform the above exercises (with a little more stress to sensitive wrists) but is also great for squats and bench press...two all time classic weight lifting exercises that, IMO, are not nearly as comfortable to perform with an EZ Curl bar.
Some food for thought: If you have no wrist issues but extra money to spend, you may want to add an EZ curl bar to your straight bar collection to vary the angle and muscle fiber recruitment. If you have a lot of wrist/forearm issues you may want to invest in an EZ curl bar to provide greater comfort while you lift. If you cannot get both, head over to a fitness supply store and check out an EZ Curl Bar. Practice squats and bench press with it (along with other exercises I have mentioned here) to make sure you will be comfortable using this curl bar for your overall barbell purposes.
Hope this helps!