I love both. One is not better, they're different. The Orsay is much bigger and has a much larger variety of artists and art periods. The Orangerie has the enormous Monet water lily paintings. Its been a while, but it seems to me that both times I went to the Orangerie, there were quite a few works by Cezanne in one of the other galleries. There was a small exhibit with dioramas of a major art donor's apartment which were really fun to see, especially for my 20 yr old daughters. And the second time I was at the Orangerie there was a special exhibit of Grant Woods which we felt was funny because we live in Minnesota and at the time, both my daughers were students at Iowa colleges, where you can find MANY Grant Woods paintings. So to go to Paris to see paintings loaned from Iowa was amusing.
I can't speak to the tickets, I was in Paris preCovid and I think Paris is busier now, and the process for acquiring tickets likely different.