G'day David, there are few pieces of information you need to know before choosing the right pump for your requirements. The below info should help:
The Maximum Head rating of any pump will tell you the maximum height the pump can pump to. So you need to know how much height you will need to draw from the water source up to the pump (suction height) and how much height you will be moving the water (uplift). For example, if you needed to draw up water 5 metres from the water source to the pump, then move the water from the pump up a gradient of 25 metres, then you would need a pump with a maximum head greater than 30 meters (5 + 25). Also note that as water moves through the hosing and the bends it will encounter friction, causing some small additional head loss - so you should need to choose a pump with maximum head larger than your height pumping requirements. Then you'll need to consider what flow rate you want to move the water at...this is where Pump Charts are important to consider (see product brochure) because delivery capacity falls away as max head capacity is approached.
Overall, work out your suction height + uplift, then choose a pump with max head capacity to more than handle the sum of those heights, and a pump that satisfies your flow rate requirements.
In terms of Trash Pumps; yes many people will use a Trash Pump over a standard Transfer pump for moving clean water as Trash Pumps are built with larger impeller veins and on a like for like basis will possess greater pumping capacity.