Philips 1648 is a rebadge of BenQ 1640, and all three including PX-740 are identical hardware wise. The only different is their firmwares, they have different writing strategies. However since they are identical, you can cross-flash to one of the firmwares. You would void the warranty if you crossflash, but I've seen many members crossflash drives without any problem.
I would choose whichever the cheapest and flash with BenQ latest firmware that supports PI/PO error checking with Nero CD Speed. PX-740 does not support any error checking.