Its like this. many ways to accomplish a task. You need to take the task apart and put it into context.
The alky system is three parts
1) Hardware= Tank, fittings, pump, lines(hoses), nozzle, filter
2) Electrical= Controller, wiring, termination, sensors
3) Support= vehicle specific, users, results.
Get the above 3 points and break them down individually. You will come to your own conclusion as to where your money goes.
The multipiece diaphram that comes in the smaller Shurflo's will fail with straight alcohol. It "IS" the reason of so many failures from the pump and the reason a lot of companies are moving to the Aquatec pump. The larger Shurflo's have a thicker single piece diaphram that is resiliant to straight methanol. We currently use, and have been using the larger version Shurflo's and our own custom valve for the last 6 years..
The diaphram material on the Shurflo and on the Aquatec pump is made of Santoprene, so there is no majic. But when you obtain the least expensive Shurflo pump they mfg and expect it to work wonderfully.. it wont. Its like buying a GEO and expecting a Cadillac. There is a write up describing the pumps on my site,
Safety should be the number one consideration when installing a device designed to deliver a liquid under high pressure
Good luck with your choices.