Another recommendation for LPD if tray life of the working strength dilution is important to you.

The liquid is expensive (but very convenient and lasts a long time) while the powder is not. Note that the powder mixed to stock is half the strength of the liquid so it isn't fair to compare the prices directly. Powdered LPD is mixed to stock then standard dilution of 1+2 where the liquid is diluted 1+4.