Actually, fiat bookies have lower odds in general, but with promotions and boosts, they can have more. And I'm a Sunday, very casual punter, as I have to keep explaining. I really don't have time to bet across 10 or 20 bookies, but I might if I had the time.
There really isn't any point in comparing odds at 20 different bookies if you don't play for the highest stakes (1000$+), you just add more stress without much benefits. I have accounts at 4 BTC accepting bookies and 6 fiat bookies. At the moment I actually use only one fiat bookie and 2 BTC accepting bookies. That one fiat bookie is only left because it still has much better interface than all BTC ones and more sports/match options than BTC ones. Hoping the need for that one will disappear soon

Sportsbet has come furthest to close that gap but there is still room for improvement.