The Flute Concerti of Op.10 on Naxos is a must have for Vivaldi fans. Really excellent performance and sonics.
My favorite Vivaldi is La Stravaganza by Rachel Podger done in both CD and SACD (12 violin concertos). I have the CD but plan to buy the SACD. It can be found at elusivesound.com and other places. The sonics are excellent and the SACD was rated 10/10 a few years ago by Absolute Sound. Great music as well.
My favorite Four Seasons is Christopher Hogwood and The Academy of Amcient Music on the L'oiseau Lyre label. This is an older recording but still sounds very good. I have Four Seasons SACD with Isaac Stern on the Sony label, but feel that it is of more historical significance and not as well recorded, even in SACD. IMHO. I am sure there will be other opinions about other Four Seasons and I know that there are other SACDs but I have not heard them. The La Stravaganza is a keeper, though.