I don't know about all this...
I personally really didn't like the memory foams that came with the Layla's. It seemed to muffle the highs and create bloated bass.
All foam tips do this with IEMs as they suck up the high frequencies. Plus Jerry Harvey included the silicone tips as the standard tips. If he thought the complys were the original tuning he should have stuck them as the default tips. I figured he included them for people who have trouble getting seal with the silicone. I do agree that if you're having trouble getting a good seal/fit with the silicone then you're forced to go with the memory foam, but if you get wonderful seal and sound from silicone... to my ears I prefer that sound and feel like it's more neutral/reference than foam/complys
Anyway... everyone has different ears and different tastes. For me the original silicone tips are the bees knees and create my own idea of reference sound with the added benefit of velvety lushness that is evenloping. This characteristic does not come from coloration of the frequency response, but just the sheer capabilities of the 12 drivers to produce incredible dense/rich tones without using the trick of mid-bass bloat tuning.