Preliminary results show that the two are comparable, although Crixivan is in a supposedly more potent drug class. People with viral loads above 100,000 also did equally well. Another non-nucleoside analog, Sustiva , has already proven its equivalency to Crixivan. That's Highly Active Anti-Retroviral Therapy. Other studies have found similar results.
People generally switch because of side effects.
Ziagen is the most potent nuke.