i go magtran as it uses both of heatrans powers and can OHKO any 100 HP pokemon, it's also got a better stage 1, more HP, and doesn't suck horribly without heatran LV.X.. so i vote magtran
Not nearly as good, no matter which you're using... the other 2 just do more for less...
I vote InferTran, ShinyMew pointed out why SF and MD Apes are so great... and if you REALLY want to use burn, you could use MD Monferno (although you won't use it much). I personally like the MD one better tho, OHKO anything in the game with 2-2 Heatran! (but that might just be because I don't like spread...)