You might want to take a look at this 'shoot-out' between SRCs... IF their methodology has delivered accurate results, it would appear that there can be quite a difference between SRCs, with 'dedicated,' standalone SRCs delivering seemingly better results as a rule than the SRCs included in some major DAWs -- although they test the PT Tweakhead SRC and it looks quite competitive from their results.
http://src.infinitewave.ca/
[The interface on their Flash display gui takes a second to figure out. There are two displays, so you can compare two sets of results. Use the pulldowns to pick an SRC for each, and then use the other pulldowns to change the "display mode.")