you can see on some of the cheap kits >$300 the fittings are rather small compared to the brand name ones which use earls fittings. I dont like the idea of putting any extra restrictions in the oil lines than there has to be.
Oil filters do put some restrictions on the system but there are websites out there that have tested all the brand name ones - incl. K&N and Purolator (which i use) and these give the least restrictions to flow, as well as the better design for filtration.
I dont normally boot my car around for extended periods, but the other day i did (wasnt a hot day either) and within 5 - 10 mins oil temps shot up to ~95 deg. Water temps stayed around the usual 85.
I wont be fitting a cooler without a thermostat, as i believe the info about cold starts, as well as daily driving i want my oil to stay around 85 as well. There is an operating range for oil, and the quicker i can get my oil there, and keep it there all the better i say.