I think you would find that either pump would seem to work well and pull decent vacuum, but when using the smaller 4008 pump, if you have too many taps you will not get maximum vacuum (and sap) at peak sap flow times. If you care about getting the highest vacuum and sap production possible, the 4048 pump is a better choice if you have more than about 100 taps. I saw a consistent 25" at the pump this past season on my setup with a Shurflo 4008 and 82 taps when it was flowing strong. If I doubled the number of taps on the same pump, my guess is the vacuum would drop by a few inches, and amount of sap would drop proportionally. A customer in Wisconsin found this to be the case in his sugarbush also. So the tradeoff, is it worth an extra $100 for the 4048 pump to get more vacuum and more sap.
The 4048 pump draws about 50% more power than the 4008 so battery life will be shorter. My 4008 pump will run 35 hrs on a deep cycle marine battery. i would expect a 4048 pump to run about 24 hrs under the same conditions.
Dave