Unless the transformer is only feeding a single load I'd use a 225A main breaker to feed a panel.
Most of the panelboard manufacturers have standardized their bussing as 125A or 225A so there shouldn't be a cost impact.
The only time that I would choke a 75kva transformer to 96% of its rating is if I'm using fuses and there's not enough room to mount a 400A switch fused at 225A.
