my opinion,acca = icaew both same syllabus and same qualify(pro in audit/tax/accounting,maybe also in finance?)
cima different from above both,more concentrate on management part/strategy/business plan or else?....but lack of audit part...which more prestigious,em...actually i don know ....some said icaew,some said acca ,some said cima....i think this is really depend on the person...
the oldest accountant bodies is ICAS,1st royal charter in the world,maybe u can say icas is the most prestigious one...

ACCA syllabus will going to slightly changes in 2014....