Time/fuel permitting it is always a good idea to discuss the options with company reps as they should have a better picture of facilities/loadings of alternates/crew plans etc and access to more weather info than we have.
As above, however, the final decision is with the 'responsible' person, the Captain. I recall a bright young thing in BA Ops trying to get me to divert a Cat I 737 from a foggy LGW to xxx, when I had in mind yyy. "NO, they said, the weather at xxx is good" and read me the TAF/ACT which were indeed OK. I said "Is there anything else on the met for xxx after what you have read me?". "Oh yes", he said, "It says 'Tempo 400m, OC 100". Guess where I went....