Evaporation loss formulas
There isn't much to choose between them. They are both variants of the same general equation. They both take account of the three main variables: temperature, rate of advective removal of moisture (proportional to surface wind velocity), and difference in vapour pressure (which can be related to humidity). In countries using SI units there are several other evaporation equations along similar lines Some other equations do not take adequate account of advection (the 'v' parameter), and hence I would advise against using such equations. 
Strictly, the best equation, favoured by FAO, and in a slightly modified form by the American society of Civil Engineers, is the classic Penman-Monteith equation:


from https://en.wikipedia.org/wiki/Penman%E2%80%93Monteith_equation
But this is a pain to calculate, so most people, including myself, put it in the 'too hard basket'. 
Whatever equation you decide to use on your spreadsheet, be aware of potential errors from ground conduction (underestimate of E), higher salinity (depresion of E), and boundary effects, especially in areas of high advective exposure.