I am always concerned about cancelling a trip booked via OTA. On united.com, it is easy to reuse the credit on a future trip. Not sure what happens with the flights booked via OTA especially if the OTA booked two one ways instead of a RT. Do you deal with UA directly to reuse the credit or do you have to go through OTA?
Other than that, I don't find much difference in the trips themselves. I have saved almost $1000 dollars booking a packages on Orbitz getting the exact same UA fights and same apartment. For me it all about dollar and cents. The unknown comes if you have to cancel the trip or if there is an IROPS.