According to Kenne Bell larger fuel pumps will heat up the gas and make it less efficient hence why they recommend their Boost-a-Pump kits.
I am not running a Boost-a-pump myself, but the way they explained it made some sense so I decided to not go larger than 190 lph for my setup (see sig).
I notice that a lot of guys here seem to run very large pumps though, so perhaps it doesn't really matter.
Anyways, here is what KB says about the matter:
http://www.kennebell.net/KBWebsite/Common/pdfs/FuelPumpTech.pdf