I just bought the Aqueon mission style cabinet and canopy today for my 75G. It's the same one that I had on my 180G reef tank before I took it down. It held up very well, looked good and an extra bonus was that the stand is higher than the typical store bought cabinets so there was never an issue with how tall anything underneath needed to be. The canopy on this model has the entire front opening up on a piano hinge to allow for easy cleaning and accessibility. I have also had the Aqueon Modern style on another 75G tank, also without issues.
I think any custom made one, if made correctly, will definitely be more sturdy than any store bought, but I have never had a problem with any of the Aqueon stands that I have had, knock on wood.
75G high tech
Back to a sump for me!