If all claims are exact (which on ebay from chinese sellers is a gamble), theh 405nm 1500mW will greatly outperform the blue laser.
That being said, thhe blue laser module has a driver, fan, heatsink included all in oone. The single 405nm diode does not, and you will need to purchase those seperately.
If it were me, I would DIY all of the parts, because theres NO WAY it's worth $240 USD for a 2W blue engraving kit.
PM me if you want me to build you one for half the cost.