The $7.99 "Wipeout HD Add-On Pack" adds the single-player mode from that game along with all the online tracks, 12 new ships, and PS3/Vita cross-play for 12 tracks not previously included in 2048. The $7.99 "Wipeout HD Fury Add-On Pack" adds 12 more tracks, another campaign, and 24 more ships.
If you want to buy them both together, you can do so in a $12.99 bundle. Or, if you already happen to own one or both games on PS3, you can just download the Vita DLC for free. Conversely, if you buy one or both of these, you can get the PS3 versions for free.