I believe it depends on what kind of accounting you want qualifcations in.......the short answer is that if you want a good all round knowledge then ACCA is your best bet as CIMA is more specialised. I can't remember the specifics, but I think that CIMA is more management accounting. I hope that helps.
acca is a certified accountant, cima is a management accountant, katejess. Unless your planning to specialise in being the management accountant to a car firm for example, then go for acca which is generally accepted by most accountancies AND businesses wanting their own accountants (except the top-notch companies who will probably insist on Chartered Accountants) - both have roughly the same degree of difficulty (i am told)
ACA is the most valued qualification in practice (it does lots of Tax) and does go a long long way in Industry
CIMA is excellent for industry. Exams can take a while to get, but endless tries is a good thing :-)
ACCA is becoming more common and is a good all rounder
Depends what you want to do and where you can get training.