Bitcoin-qt is NOT for everybody.
Direct quote from the bitcoin.org download page: "Bitcoin-Qt is a full Bitcoin client and builds the backbone of the network. It offers the highest levels of security, privacy, and stability.
However, it has fewer features and it takes a lot of space and memory."
In regards to online/light wallets, again it's security vs convenience.
Hm...true but not completely true.
Putting your btc in a casino or exchange is discouraged due to security reason.
But at least for the above three options, you have full control of the private keys, and it is not that much of a security concern.