If the pump drive is lost then, unless you have some sort of warning device, the first you will know of it is when your oil pressure drops to zero and the engine goes bang. Some people have, I believe fitted either a micro switch or a light sensor to tell if the belt breaks and then lights a large warning light on the dash - if you react quick enough and shut down then you should save your engine - the more oil capacity in your tank, the longer you have to shut down.
I can second frankyknuckles' findings regarding capacity - max 5 litres without Apollo or oil cooler.
I believe some early adopters had breathing problems with the Pace setup but it may be resolved now.
To me the Caterham system is probably the easy choice (hence why I went for it) as you just order the kit from Caterham, curse the cr@ppy instructions and get on and fit it. It is also a very neat install when complete - the pump fits where a power steeering pump would have gone thus utilising standard fixings and the tank in the bellhousing is a neat touch.
With the Pace system you are one of a much smaller group of users but perhaps it is technicallly a "better" system. The cost difference is not nearly as much as people say once you have added up all the bits that you must source from different places for the Pace system but there is a saving.
If I were to make the choice now I would probably chooise Pace as I will shortly have a highly modified engine. If I was fitting to a standard Caterham engine then I would probably stick with the Caterham DS kit.
Yellow SL #32