Silicone baking liner vs. Parchment: I've tested and retested and found that on average I get the best results from parchment. The precut sheets you can find online and in bakery supply stores in particular (they're great). Parchment from a roll tends not to lay flat (even with a little extra macaron batter tacked to the corners to help it stay down) and that can sometimes make my macarons look a bit more like amoebas than round cookies.
I have found that parchment produces taller compact feet, the Silpat baked cookies' feet tend to be shorter and a bit ruffled. In my kitchen, at temperatures under 300°F, the cookie's bottom tends to lift off the slipat and cling to the top of the shell, making a little hollow under the cookie. This makes them easy to remove and the macs don't have a gap between the cookie's insides and the top of the shell. Which if you're having trouble with hollow at the top macs, could be a good thing.