Which do you prefer ? I've used Merit for the past few years and have had good success even though the weather conditions the past few years may not have warranted a challenge for the product. Have been considering Mach2, since watering requirements are less and issue. What's your feel on these products, have either failed you? When do you start applying your control? What kind of pricing do you get on these products? Usually both run in the low $40 range here. Thanks in advance!