They're both smooth to the touch. Labella flats are the only I've ever liked cuz they're super smooth. Pressurewounds are fantastic. As smooth as roundwounds get. Really the best of both worlds between rounds and flats. Halfrounds always feel sticky to me. If you're looking for dull and dead but brand new, I think tapewounds are the winner.
GHS and Ernie Ball make the deadest strings I know of.
Ernie Ball flats (which are identical to Chromes, btw) are very bright and clanky when new. GHS Precisions, on the other hand, are pretty mellow even right out of the pack.
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