When I went for my only airline assessment it didn't seem to matter where anyone did the MCC and at the end of the day an MCC is not about what aircraft you do it on but getting a fundamental understanding of how to integrate and use all the crew to your advantage
My sim partner probably paid less than 50% of what I paid for my MCC and it didn't hinder him in any way at all with getting the job
I would agree doing it on a full glass cockpit setup will be more beneficial like an NG or 320 as most flying these days will be glass cockpit