I vote for two crates, with a caveat! Sometimes, you need the dogs to share close space together - whether its the back seat of a car or a crate.
I got Bacca at 8 weeks old and crate trained him from the start. I got Indy at 10 months and he was also crate trained.
Then it came to bringing both dogs up to the cottage every weekend by car and by boat. Two crates were not practical.
So they boys learned to share the back seat of the car and a crate on the boat ride over to the island cottage. We've never had any issues with this. They both cram into this large soft-sided crate readily enough. It's only 10 minutes so they put up with it readily enough.
All to say that you need to ensure that you can have your pups tucked into close quarters together sometimes.....without one or the other trying to dominate...