We are custom building a new 3D printer, intended to be high end.  Printer controller board is custom, based on an ATmega.  We will also have a Raspberry Pi 3 on-board to control the whole printer itself.

Question: Does anyone have any advice or recommendation on firmware selection, e.g., Marlin vs Repetier vs Teacup, etc?

Standard Goals: Good speed, good resolution, reliable, etc.