Optical: ProChrono with Caldwell light bars. The light bars vastly improve reliability.
Magnetic: Magnetospeed
Microwave: LabRadar
I own all 3 having acquired each as they came out.
The above comments are accurate about the virtues and gripes of each type.
The most cost efficient is the ProChrono which has always been a good optical solution IMHO especially with the light bars.
It even registered 95 fps when I shot a rubber band across it with my fingers in my study/library.
It's the biggest PITA of the lot to set up especially at an indoor range with others present.
The Magnetospeed works fine for rifles and some revolvers but won't even mount on short revolvers, pistols, or doubles.
Very simple and easy to use when you can though.
The LabRadar is the ultimate $olution. If you can afford it you will never look back.
Getting it to trigger reliably going from one firearm to a different one is the main challenge.
Once you get the settings for each down pat it's all smooth.
I took the batteries out of the other 2 so they would not rot and ruin the equipment.
I had an early digital camera destroyed that way (leaking batteries).