I'm not trying to say they're exactly the same but they have similar characteristics and fill a similar role. The difference is the scale at which they preform. The Puma is like the Jackson of light vehicles. The Jackson is like a large Puma for use against medium and heavy armor
Like Vipper said; not really.
Firstly, the Puma has only 50 range, compared to the M36's 60 - conveniently, 60 range is the same as (almost) all ATGs, so the puma needs to be in danger of those to fire at a tank, whereas the M36 will be just at the edge of an ATG's range.
Secondly, at max range (50 vs. 60), the Puma has 80 pen, meaning that it'll bounce 39.5% of the time against even the "lightly" armored M36 (80 pen vs. 130 armor), whereas the M36 will pen even a panther's front armor 84.6% of the time (i.e. 15.4% bounce chance).
Thirdly, while the puma is more mobile, it has 0.5 moving accuracy multiplier, whereas the M36 has a 0.75 mult - that's 50% more accuracy when on the move. That makes the Puma pretty bad when chasing vehicles, whereas the M36 doesn't really have that problem.
So, the Puma needs to be in ATG range to hit anything, has more than twice the bounce rate against fairly lightly armored vehicles, and is 50% worse when moving. Interestingly, those three categories are the ones people want the M36 nerfed in (range, pen at max range, moving acc.).
Since it'll be brought up that I'm comparing an LV's pen vs. a medium to a medium's pen vs. a medium, the M36's chance to pen a Tiger (heavy) at max range is 73.3% (26.7% bounce). That's still a 57% better chance compared to a Puma vs. an M36. That results in an even bigger effective DPS difference when factoring in that 50% better moving accuracy.