I haven't seen one BTC sports book that offers better odds than Nitrogen, so that's that. Nitrogen offers the best odds unless the sports book's rep comes in here and refutes that by showing their odds. And I call b*ll sh*t on your claim.
The selection of sports is arguable but their list is still really excellent imo.
Fairlay has better odds than Nitrogen on many sports and many games. However, they are not a real sports book and
instead a prediction market. They use several market makers that make sure that the popular league markets
are seeded with enough money.
E.g. the first NFL game I looked at (decimal odds):
Green Bay packers -3
-Nitrogensports (3 BTC max bet @ 1.905 odds)
-Fairlay (3.253 BTC max bet @ 1.938)
As you can see, you can bet slightly more at Fairlay and have better odds while doing so.
This is similar for most other games as well.