Firstly, as one of the high-end models, the SP-510A has an maximum applicable PCB range of 510x510mm, which is different than another high-end model called SP-340A. The SP-340A only has a maximum PCB size of 510 (optional 530) x 340mm, which is more suitable for a smaller PCB board size.
Then, Electronicstalk recommends the SP-510BTB for any dual-rail printing requirements. The reason is that it can double the printing productivity while cost at only one machine with less space occupied. Lastly, for the small PCB size requirement, there is the model of SP-340B suggested.