I think you should be asking the following questions.
1. at the location you are working at, what plc's do you have?
of those plc's, which ones do maintenance like the most?
why?
2. what plc distributors are in the area?
3. what kind of support do they have?
good, so-so, little?
4. what inventory do they have?
if we have a breakdown, can we get the parts quickly?
5. what is the distributors reputation?
6. how easy is it to learn their programming software?
everyone on this forum has their own favorites, so you will get several answers.
I learned Omron S6 first, then allen Bradley slc 150, Minerak, wago, plc2, GE,
slc500, plc5, Mitsibichi. now its logix 5000.
I worked for several oem's and we had to wear many hats.
regards,
james