Generally, angel investors do not invest in deals greater than $1 million whereas venture capital firms typically are not looking at deals under this amount. As an angel, you make your own decisions as opposed to a board or group of people representing investors that have pooled their money.
Entrepreneurs often expect that you may be more involved in the business and may provide assistance in ways that venture capital firms do not. You also do not typically own as large a stake in the company as a venture capital firm would. Another benefit of being an angel investor is tax exemption for capital gain.