There are many blogs out there comparing the two different CPUs. However the reason why I chose the Z80 over the 6502 was it's simplicity (my opinion) and documentation. The Z80 requires a lower number of components to get started compared to the 6502. There also seems to be a better supply of Z80 components (They still make them!) than the 6502, so Z80 components are more easier for me to obtain (I’m sure your milage might be different). Also, since this is my first major build, I wanted to keep it as simple as possible and have something up and running as early as possible.
My nickname is Philbywhizz, or 'Whizz' for short. So combining 'Whizz' with the 80 from the Z80 CPU I came up with name Whizz80 and it has stuck.
Why not ask one?