Which Loop Formats?

Thinking of buying some loops to work with stock Sonar X3 instruments.  Is one format 'better' than another?  I need to stick with rex or wav formats, right?
 
Thanks and Happy Thanksgiving!

rex and acid wav. Both are previewed by media browser at project's time (and pitch if any). Both can be dragged from media browser onto track view and appear as groove-clips with rounded edges (can be duplicated by dragging). Beware, some loop collections are RAW, simple wavs, not acidised, you realize it because they have not rounded edges when in track view. For both rex and acid wavs you double-click the rounded clip and this opens LCV (loop construction view), which sees the slices and can pan, pitch.shift, amplify each slice (e.g. silence some slices, so to grab only some slices containing pro sounds to steal and drag to a sampler for creative use).
 
Rex/rx2 are better than acid wavs because you can open RXP or Dimpro and drag the groove-clip from track view to either plugin interface, then with the note button (top right) you drag "midi stairs" onto a midi track and you can swap slices by midi editing. Actually I complain about DimPro, since Sonar supports both acid and rex while DimPro only rex, that's not fair because big samplers support many formats.
 
Finally I live in Sonar X1, if you have X3 you should also benefit ARA support for Melodyne, which complements audiosnap beautifully in mangling original loops even simple wavs.