Fixed Deposits versus Unit Trusts

I am pondering should I put the bulk of money into the slow and steady FD (Fixed Deposits) or takes risks and invest in Unit Trusts which hopefully bring in more returns. Unit trusts are a group of shares managed by a fund manager. When you put your money into unit trusts, about 5% is already deducted from the principal for the fund managers. This is quite a huge amount but the proposed returns are supposed to be better. This is just a projected return. However, I feel much safer to put into FD for less but sure profit. FD return is around 3.7% a year which is not too bad. So between the two, to avoid less headache, I rather put into FD for a less but sure return.