Pinnacle is awesome. I hear Betfair is good but I live in the US so I know nothing about their limits and types of bets and action etc. Pinnacle takes very decent limits for a sport like tennis. Allow you to hit a match more than once. For the later rounds, they offer set betting. And they actually have the matches before they go off. And if a match hasn't gone off and it is off the board, you can email them and they will put it up promptly. Like everything else, they are simply awesome. It's great to see things like weather or how people responsd to waiting around or to "create" your own parlays rather than ripping you off like other books. Finally they grade your matches right away. The only thing I wish is if a match was suspended overnight, they would have lines up. They could even copy of betfair's lines and adjust accordingly. But that is getting too picky. Incidentally, they are doing very well this week on the New Haven tournament judging by line history at tip-ex.
5 Dimes is so overrated. Their limits suck. And I find their games option worthless and for a book that's supposed to be considered great for the bigger sports they are not even close to Pinnacle's leagues. I find them worthless except for the odd future. I have heard they are giving money away this week in qualifying from what I hear but I don't bet qualifiers
365 is only American books that have interactives. Needless to say they have ludicrous juice, but interactives everyday and they allow you to hit it and set betting at ludicrous juice and bizarre limits. One match for set betting will be like 350 limit risked. Another will be 1100. Really strange WSEX might have them for like the final matches i but only good for Grand Slams. It's bizarre but I can't seem to beat 365 in tennis.
Santo mentioned Olympic so I will give it a look. I am surprised that Mansion being in Asia doesn't seem to care about the tennis market. Hope this helps.