There is no easier sports to wager on because the odds adjust themselves accordingly. The only factor you should consider is whether the odds given are higher or lower than their chance of winning and there are good opportunities in any sports but at the end of the day nearly no one can win consistently and profitably.
But some say there is faster money in tennis example live betting on serves etc so from sport to sport there is fast betting action here.
It all depends on individual interest because I don't follow tennis game much so I may not be able to make an accurate guessing if I bet in tennis. But I'm good in cricket match betting because I know most of the world cricket teams strengths and weakness, so my guessing will be more accurate, but still, we need some luck to support our guessing. I made some profit in cricket match betting earlier when directbet site was there but now stopped cricket betting.