You are correct, in that both options are viable. I think what you will find, as you do the research, is that it is not the overall run time that determines the life of the pump, but rather the frequency of starts / Stops. If you are using the pump for nothing other than irrigating your lawn using an automatic system, then a pump only solution would be what I would recommend. Most control timers have a Master valve/Pump channel, which in combination with a pump relay will turn your pump on when the timer starts irrigating, and off when it is finished. One start per cycle. Be sure to do your homework on the design, and match the output of each zone, to the amount of water output by your pump.