Use the search thing for more info, there's loads of threads which get really detailed and will
help 
but the long and short of it is that it's down to personal preference.
Split R is 50% recirc & 50% blow off so can be quite loud and 007P is fully recirc. The 007 does get loud with a remap and open cone air filter however.
If you expressly want a 50/50 valve then the Turbosmart Kompact Dual Port comes highly recommended over the Split R. Remember that if you set the 50/50 valves too loose or block off the recirc port, you will most likelt get limp mode.