Both were faster. DRAM was a little cheaper, but required more circuitry to handle refresh on most CPUs making it a wash cost-wise on some designs. Typical woz engineering got the cost of the refresh circuitry down to where DRAM made sense economically on the Apple ][.
Interestingly Z80s had DRAM refresh circuitry builtin which which was one reason for their prevalence.
And for the Z80: also that it only needed GND and 5V. The 8080 also needed 12V. And the Z80 only needed a single clock phase -- the 8080 needed two. The 6502 also only needed 5V and a single clock input (the 6800 needed two clock phases). The 6502 and Z80 were simply a lot easier to work with than most of the competition.