Currently, I have a 30mm barbell (180cm, 10kg, fixed sleeves) with 30mm plates that I bought a while ago. Now I’m nearing a point where I’m running out of plates to add and I need to buy more. I could:
A. buy two 20kg/45lb 30mm plates
B. buy an entire new set of 50mm barbell and plates
The second option is much more expensive of course, but my understanding is that 50mm barbells are preferable. I’m guessing the main benefit are the rotating sleeves and their effect on the wrists?
At which point does it become “necessary” to use a 50mm barbell? Is there some rule like “up to 150kg it doesn’t really matter, but above that avoid 30mm barbells”?
I would recommend buying a near-competition spec barbell and plate set so you can train effectively for the rest of your life.
Fixed barbells won’t work for long due to loading issues (and how they hold up over time) and I wouldn’t use them for training at any point if I could use a standard barbell.
That said, no one knows when any bar will fail or when you MUST move to a standard barbell, but if you care enough about your training to post about it on an Internet forum…you probably deserve a legit barbell, right?
Thanks for your response! You’re right, I deserve The Best A Man Can Get 
And the 45lb plates make up a huge part of the total cost anyway, might as well go the 50mm route today.