I have been using LoadRunner for more than 6 years. It is the industry standard for performance testing and supports a wide range of applications.
It may be difficult to use it at the beginning. But once you start using it, you realize that it is a very powerful tool. The free version comes with 50 users but if you are looking for a much larger load, you may have to take the cost into consideration.
As far as JMeter is concerned I have used it just once. But my preference would always be LoadRunner