Contact. I just got some 27g, but much as I liked my previous 28g build, this one is better.
Used the 27g last night. 7 wraps around a 2.5mm bit @ 1.1ohm in my Taifun GT V2. Vapor production and warmth is good but I feel I get slightly better flavor from 8 wraps of 28g around 2mm bit @ 1.2ohm. Still need to play with it a bit more but pretty good for my first build with it.
Lately, I've actually been experimenting with thinner wire like 29g and parallel 30 or 32. I like that the thinner wire heats up and cools down faster, seems to gunk the coil less, but I've not been able to get the same thick, velvety vapor from my 28g builds.
I have 7 wraps of 29g around a 2mm bit @ 1.4ohm in my Eviva-T and 6 wraps of 29g around 2mm bit @ 1.2ohm in the Phenom Lite.
I've found I really don't need to go below 1.4-1.5 ohm in the Eviva-T with the little ceramic cup. Still trying to find perfect wire/ohm build in the Phenom Lite.
Can't believe I've had the Calix now for over a week and haven't even touched it. Just not enough time to mess with all the new toys.