Now that Standard and Extended are separated, Extended format is no longer the 'best' for playing DT's. They're two different formats with two different competitions, meaning that they're both as viable as each other.
As far as Extended goes, I've won with Montana, Uppers and Sentinel, so they're all very good. I'm also pretty sure that Piranas can work really well, and you could even give Rescue a go. Technically any deck has the potential to win (I know there have been some inventive ones in the past) but just by nature, I have followed the crowd and gone towards using strong attack manipulation clans in tourneys.
Standard is a slightly different story just due to the smaller card pool. Because I've become comfortable with attack manipulation clans, I still tend to lean towards them in Standard. I believe the highest rated preset right now (at least last time I checked ) is an Uppers/Junkz Standard DT deck. I got a win with it on my first attempt, but the one who published it got the absolutely insane score of 769! It works well.
In Extended, I ALWAYS use mono.
Mono just secures the bonus right ?
DT's changed a lot since the past because in the past it was more easier for everyone now they made it more harder.
Not only does going mono secure your bonus, but it also allows you to take advantage of some very good support cards, such as Avola, Oscar and Moses for Montana, and John, Martha, Coby and Sammy for Sentinel. That's just off the top of my head.