well biked

If it's improved modulation you want, the levers may have more to do with it than the brakes. Shimano's servo-wave v-brake levers (currently available in XTR, XT, and LX) are very good for this, follow the directions for setup (i.e., remove all "adjustment blocks") and you'll be able to feather the brakes more affectively, as well as increase your braking power because of better leverage than with typical v-brake levers.......beyond that, the highest end v-brakes (Shimano XTR, Avid Ultimates) are about saving weight and bling factor, not increasing braking power. The one thing the Shimano XTR and XT have (not sure about LX but I don't think so) that the others don't is Shimano's "parallel push" design. It adds some complexity to the brakes, but from my experience it works great at keeping the pads parallel with the rim surface instead of traveling in an arc. Of the Shimanos and Avids, if you want really good linear pull brakes, I'd look at the Shimano XT's and Avid SD-7's. Combine those with some Shimano servo-wave levers and your friend will definitely have better brakes-

edit: if you do go with servo-wave brake levers, be prepared to also invest in some brake boosters, for the rear of the bike particularly. The increased power with the servo-wave levers will likely cause your seatstays to flex noticeably, which not only defeats the purpose of the increased braking power and modulation, causing fade, but it's also probably not so good for a frame. With brake boosters, the stays will be rock solid and the brakes will provide predictable modulation, as well as excellent power-