I was curious as I'm booked at a trial resort and following the rollout in Disney, and as I am booked at the Royal Pacific in April, so I called Universal's central number and she said that she didn't really know the actual policy but that guests can leave pets unsupervised in their room as long as they are crated and don't disturb other guests. But since she didn't know the actual policy, she gave me the direct number to the on-site concierge at the Royal Pacific. The concierge told me that the form I attached below (linked on the Universal website) is the policy that guest traveling with dogs sign upon check in. She said that guests leaving dogs unsupervised in their rooms is just "one of those things" but that the guest "technically is in violation of the policy", however she said that they respect guests' privacy so security will only enter a guests room and put the dog in "time out" if it is disturbing other guests. The words I quoted were her words, the rest is paraphrased.
So take it with a grain of salt, it may be who you speak to, which at times has been my experience with Disney. In either case, it sounds like Universal has a good track record of keeping pet friendly and non-pet friendly fairly separate, so maybe there are fewer issues? My understanding and I don't know what poster said it, was that the Universal resorts were built with pet friendliness in mind, so maybe they can deal with issues easier if they arise. Like I said above, I agree with
@2Kds2K9 that it seems more convenient to come back for breaks in Universal, since more appears to be in walking distance.
https://www.universalorlando.com/web/en/us/files/Documents/LoewsPetAgreement.pdf