There are quite a few differences between the 25 and 27 foot trailers. The International was pretty much a trim package, it would include such things as a relocated oven, different trim, and of course a spiffy "International" badge.
The 25 and 27 have completely different interior configurations, from where the fridge sits to the type of bathroom. A big difference is the 27 could be ordered with a rear bedroom (very rare option), and the 25 was center bed only. Both could have twin or double beds, but the fridge is much smaller in the 25.