Why does everyone talk about weight as if they're scientists? Bone density, muscle mass, time of day, meal or no meal in belly... you don't know these things, you can't talk about an athlete's weight from photos. Weight varies a lot more than size during a day.
Jones is much bigger than Silva, just as he's been bigger than all his UFC opponents to date. Weigh in photos look sort of competitive but come fight night, he dwarfs opponents and is noticeably stronger than them. I believe there is a lot of science behind Jones making the weight as he gets older, but fair enough, he has made the lifestyle changes and sticks to them. Can't say the same for the other top LHW's, except Gustaf and Machida. Lyoto always comes in under 205lb nowadays with his consistent lifestyle, whereas Jones still has to cut some...
Silva is the guy to beat Jon, bar several heavyweights, but as has already been said, he gets the moral victory just by stepping in the cage. He doesn't fight at LHW regularly, has not optimized his body for that weight, and would be fighting a young Champ who brings unprecedented strength and wingspan to the division. You could say the same about Belfort and Sonnen, but they had a lot less to lose.