When I was younger, poly perimeter worked best for me because bonding was easy and strong, and clean-up was easy, especially with tape. Being young, a heavier density and a longer hairstyle easily masked the poly. I was very active physically, and with a good tape attachment, I had no problems with lift, and swam, worked out, even martial arts. Being older now, lace works better due to lighter density of my own hair; lace lends itself to lighter densities at transition areas and hairline. Poly can last about a year, as can well cared for lace, but it's the hair itself that sheds, dries out, fades, etc., so it depends on those factors more rather than bases for longevity. Lace gives the best in undetectability, but a poly edge is better for attachment.