It is odd to do things that cost a great deal of money just on the basis that (a) other countries are doing it, and (b) more is better. Unless the main objective is to have lines that are not fully used, empty wagons shuttling back and forth, etc.
The real issues should be whether (a) the capacity is needed and (b) can be afforded.
Instead of arguing from "gut feeling", perhaps the numbers should be considered. The EA Railways Master Plan, part of the work done by consultants hired by EAC, is worth a careful read. It can be found here:
http://www.infrastructure.eac.int/The reports looks at the current railway lines, their capacity, projections in demand and essentially concludes that the current lines would be sufficient if spruced up and operated properly. The cost figures show that the SGR will not be worth the money.
There is also at the same website a report and slides of a presentation by a Japanese expert on their experiences. His conclusions were basically that (a) the current lines are adequate if certain changes can be made, (b) the obsession with standard gauge is misplaced, and (c) people should pay serious attention to maintenance, maintenance, and maintenance.
To my mind, what is required is that lessons be learned from the failures of the old railway line.