I strongly believe Heat are beatable watching the Bulls and Pacers game. And the way they defend that pick and roll, Parker would have so much options. But the Spurs were beatable judging from how the Warriors played the Spurs on the 2nd round but found it kind of an anomaly as the Warriors were just shooting out of their mind.
I think the big 3 of each team would cancel out each other, it's the role players that will dictate who will win the Championship. If Spurs reserves (Leonard, Green, Neal, Bonner, Splitter) perform and their 3's are dropping then Spurs could win it, but if they don't and played like how the OKC eliminated them last year then Heat will take it. For the Heat, you can't just discount what Birdman brings to the Heat team, his energy and frustrating the opposing players is just a good addition to them. Also, i could see Battier and Miller including Haslem can now be a factor as well. It is also kind of unfair knowing the Heat still has Ray Allen and Rashard that can make a few 3's. But we did see how the Heat looked like when their shooters are non existent and force Lebron play 1 vs 5, which i believe would be Spurs strategy in beating the Heat. If Leonard can stay on Lebron without double teams and the Spurs wing players shut down the outside 3s then it is all over for the Heat.
On a side note, the referees should learn and not call a foul whenever any player snaps back their head and flails outwardly their hands and fall. Flopping is just so freaking disgusting and hate it when players exaggerate just to get the call. I would even go the distance and have NBA call a technical on a flopping player during the game to stop this non sense.