If your city is well lit, you may not need a super bright taillight. I think having more than one light simultaneously can enhance attention grabbing. If they flash at different rates, it can help. If one is steady and one is flashing, it can help. If you have three, it can help. Then of course, this adds complexity, i.e. you have more things to charge and mount.

I sometimes use a spoke-mounted light. It's not bright but it is very much an attention grabber. I've had strangers compliment me on it. I put it on the rear wheel, as when it's on the front, it distracts me. Some have one on each wheel. My spoke like uses two CR-2016 cells which is annoying. I can get away with using a single CR-2032 cell which has twice the capacity and half the voltage, and it's kind-of OK.