I'd go 265. Save that extra weight. I don't think you'll notice a huge difference with 275s plus you might rub in the front going the wider route.
Current: AW/SO F10 M5 H&R Springs, 12mm/10mm Spacers
Sold:Imola Yellow RS4-KW V3, MTM 10mm spacers, Hotchkis rear sway bar, APR Stage 1, Milltek Catless, RNS-E, Euro RS4 Flat bottom Steering Wheel