Is it better to have a higher reduction gearbox and have a bigger pinion on the rack or less reduction smaller pinion?
The gear drives would be Alpha SP planetary 35:1 with 4,000 RPM servos if this is the way to go.
Or does it depend of a lot of other things?
If you go with too small of a pinion you will not have enough teeth in contact with the rack. This will cause a condition called jumping when reversing or sudden starts and stops. I know that there is some engineering data out there that calculates the min. number of teeth in contact based on the gears pitch.
If it's not nailed down, it's mine.
If I can pry it loose, it's not nailed down.