Id say Noctigon have a better design. But yes, the Sinkpads (at least 1st gen) are marginally taller and have twice the space for attaching wires. Which can be beneficial. Relic38 have shown that Sinkpads (1st gen) and Noctigons basically have the same performance. They are both great, just minor stuff separating them.
16mm XM-L sinkpads can easily be cut into 10mm if you want, which can be nice. But now you can get 10mm sinkpad if you want, but those are 2nd generation, at least mine are.
Various info about Noctigons in this thread.
Sinkpad 2nd generation seem to have cut corners in order to make production simpler (and probably cheaper) and to get a flat underside, you need to compensate with a bit more solder in middle. I have not seen any tests showing if this have a noticeable/measurable negative impact on performance. But the design/build is just not as good as the Noctigons....
On my previous order from LCK-LED (placed 02.11.2013) I added 3 16mm XM-L sinkpads. They were 1st generation. So I just assume/hope that these are too. Either way, I only ordered the last 6 20mm XM-L Sinkpads.