Some years ago I put money into the C fund. I decided investing that money in the US a better option. I closed the C account and had the money, 50K USD+ sent to the US directly by Provident fund. I don't recall the rate but if you in invest in anything other than AED in the provident fund and you want to use a local transfer agent, it is likely that you would have to convert all that money to AED, then convert again once it reaches the destination. That would likely cost more than a direct transfer.
The direct transfer from the Provident fund took longer than I would have thought, something like 3 weeks. I use Al Rosatamani every month and the transfer is generally 2 days, but sometimes as quick as 1 day.
good luck