Another issue to think about with 38's is, especially with trees etc in the path of most hill faces around adelaide is the couplings being so massive. I challenge someone to drag a 38 through a house or up a tree covered hill without having to double back repeatedly to unhook couplings fromm objects. It may be quick to deploy, but is more awkward in action. HP lines have smooth profiled couplings and are more flexible when charged.
Also make up time is significantly increased with lay-flat hose. This is not only wasting time (especially with work to get back to for volunteers) but also for mobility on the job. If a rapid change in location is required, and you have 4 lengths of 38 out, they have to be left and run the risk of being burn't, lost, and the appliance may run out of hose later. It takes less than 2-3 min's to make up a full 90m of hp line.
Yes they may be expensive initially, but in the big picture, lay flat does not have the endurance of HP line, nor does it have the mobility and ease of operation often required in the foothills or structures.
As for 2 lines, i have been on countless jobs where having 2 hp lines was absolutely vital, and a 38 would have been heavy and unsuitable.
I think the cost cutting of having one HP (not even - most are 25mm low pressure attack lines!) is wasting money and time in the long run.