To understand why some zones haven't received a WAP-7 or so called the 3 phase locomotives, one has to understand the basic of these locos.
These locos are high horse power locos, which are solely on manual n computerized on board.
They need proper troubleshooting too, unlike the present WAP's, which if fails down, has to wait til a rescue for a while.
Every...
more... sheds needs to b trained perfectly if handling a WAG-9, WAP-7 class locomotive.
It hardly takes 1 month or so to get trained to handle these but even then it all depends on the roster, timetable allotted n various exam factors too.
100 locos might have been given to shed, only after considering various factors which might have passed the test.
Each Loco has a LSA attached along with its POH, IOH, Check up roster too.
If RPM has been allotted 50-60 locos in a current plan, then they might have done after considering options, as Erode is already full with WAG-7's, n WAP-4's. Take a point, even infrastructure counts in before taking in new locos. A shed should b capable to handle as much as many locos it can.
A DEE/CEE n others have a hectic job out there, not like Rail fans, who fantasize about giving only a HHP to few trains n normal locos to normal express/mails.
So there's nothing prestigious out there, it depends on operational manner.
A WAP-7, WAP-4, WAM-4 are capable to haul long trains at a good speed, irrespective sectional speed permits.