I am in Sri Lanka. Agilent is very popular in Sri Lanka. I have personal experience with that brand. Also it is very popular in Australia. but Shimadzu also good brand and it is durable.
I'm afraid it's impossible to give a proper answer. Agilent, Shimadzu and several other companies are worldwide leaders in research instrumentation, so their equipment is competitive in the market. The choice of instrumentation supplier in particular laboratory and particular region depends on many factors as dealer reputation, service support and service contracts of lab's host institution, tasks to solve, availability of documentation (for instance application notes) in national language etc. (even traditions). In my laboratory we use GC and GCMS instruments from Agilent and Shimadzu and ICP-AES from Shimadzu. Latter is a good and reliable device.
Agilent is the most common in our lab, because they're reasonably priced. We got a Shimadzu LC about two years ago and people avoid using it. I prefer using Agilent equipment because it's a lot easier to do maintenance and repairs on without the help of a professional.