for most, trustworthy, it\'s Expedia. it is a huge vendor backs up a lot of other, such as hotels.com.
many online agents work the same way, they get hotel rooms from another vendor. the fewer vendors it goes through, the more reliable it will be. some bookings may even go through two or three middle man. sometimes you will find Ctrip offers rooms at especially low prices with immediate confirmation, these ones usually are more reliable due to 承包, already allotted。 those that take 5-12 hrs to confirm meaning they need to ask further with vendors whether any more rooms of specific prices are still available.
because the online hotel business model always go through middle man, this is how different problems occurs, such as the hotel doesn\'t find your room, the room is not the price you book etc. therefore, the safest way is always book direct, second safest way is to book an agent that offers direct deal with hotels, which mostly the prices are not cheapest, examples are Expedia, booking.com , Agoda.
Ctrip is not very bad. the even worse ones are in western countries if you come across other overseas forum.