The Boosted Rev I have now has exposed frame rails so you can use your favorite bike lock.
As for the rest, it's an iPhone/Pixel compared to the 2nd-tier-Android-like Xiamois. It's over-provisioned as far as motors, so whereas a Xiamoi is barely moving at its rated 14% grade, the Boosted is still pulling. The Boosted could easily exceed its 24mph limitation, so I assume that's a legal limitation. It's nice not to run at redline all the time like I do with the Xiaomi. Regen brakes are amazing. I rarely use the mechanical brake because the Boosted's regen will pull you down to a dead stop. In contrast, the Xiaomi's regen braking will haul you down if you're not in a hurry to stop, and you'll still need the disk brake for those last few feet.
In summary, if you plan to use a scooter as a vehicle, the Boosted is worth it. Not so much if you just want to go down the trail with your kids on the weekend. For that, or other occasional use, the Xiaomi is a bargain.