The Orange County Convention Center is massive. It has two separate but huge facilities.
To view the above image in a larger, easier-to-read format, click on the link below and choose the "District connectivity" table in the Pedestrian Safety box.
We attended an event at the Hilton last year. We stayed at the Hyatt because the Hilton was sold out. I think both hotels offer decent access to the convention center with covered walkways. I personally thought the Hyatt was a better hotel, but both are very nice.