maybe there are other things like the higher the crystal frequency the more EMI you get from your system, and higher power consumption, more heat generated, therefore heat sinks needed and more space, and thermodynamics. etc

Actually you get less EMI since the Crystal frequency is the same - or even less. I have less EMI from a RD2 in 6 clock mode at 16.5 Mhz than in 12 clock mode running at 33 Mhz. The power consumption vs clock frequency can be read from the data sheet, I have not had problems with heat.

Have fun,

Erik