Tau+ claims similar performance, weight, top speed to the Enertia+, slightly lower battery capacity. $5000 vs $10000 (after $1000 Brammo rebate) is a rather stark difference.
The Mμ (M-mu? bad translation?) looks sportier, but it's a little slower than the Tau. (Edit: this is wrong, both the Tau and Mu have a base, +, and Pro model with identical powertrains)
After discontinuing the XU, Zero has effectively vacated the low-power electric market. I wonder if Brammo will continue to stick it out with the Enertia - remember when Brammo was talking about selling the Enertia alongside the Enertia+?